Water in the Northern Coral region of the Northern North

Water in the Northern Coral region of the Northern North-East Coast Drainage DivisionA report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project

August 2009

ii ▪ Water in the Northern Coral region August 2009 © CSIRO 2009

Northern Australia Sustainable Yields Project acknowledgments

Prepared by CSIRO for the Australian Government under the Raising National Water Standards Program of the National Water

Commission (NWC). Important aspects of the work were undertaken by the Northern Territory Department of Natural Resources,

Environment, The Arts and Sport (NRETAS); the Queensland Department of Environment and Resource Management (QDERM); the

New South Wales Department of Water and Energy; Sinclair Knight Merz; Environmental Hydrology Associates and Jolly Consulting.

The Project was guided and reviewed by a Steering Committee (Kerry Olsson, NWC – co-chair; Chris Schweizer, Department of the

Environment, Water, Heritage and the Arts (DEWHA) – co-chair; Tom Hatton, CSIRO; Louise Minty, Bureau of Meteorology (BoM); Lucy,

Vincent, Bureau of Rural Sciences (BRS); Tom Crothers, QDERM; Lyall Hinrichsen, QDERM; Ian Lancaster, NRETAS; Mark Pearcey,

DoW; Michael Douglas, Tropical Rivers and Coastal Knowledge (TRaCK); Dene Moliere, Environmental Research Institute of the

Supervising Scientist (eriss); secretariat support by Angus MacGregor, DEWHA) and benefited from additional reviews by a Technical

Reference Panel and other experts, both inside and outside CSIRO.

Northern Australia Sustainable Yields Project disclaimers

Derived from or contains data and/or software provided by the Organisations. The Organisations give no warranty in relation to the data

and/or software they provided (including accuracy, reliability, completeness, currency or suitability) and accept no liability (including

without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use or reliance

on the data or software including any material derived from that data or software. Data must not be used for direct marketing or be used

in breach of the privacy laws. Organisations include: the Northern Territory Department of Natural Resources, Environment, The Arts

and Sport; the Queensland Department of Environment and Resource Management; the New South Wales Department of Water and

Energy.

CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader

is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or

actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the

extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences,

including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using

this publication (in part or in whole) and any information or material contained in it. Data are assumed to be correct as received from the

organisations.

Citation

CSIRO (2009) Water in the Northern Coral region, pp 53-116 in CSIRO (2009) Water in the Northern North-East Coast Drainage

Division. A report to the Australian Government from the CSIRO Northern Australia Sustainable Yields Project. CSIRO Water for a

Healthy Country Flagship, Australia. xxviii + 116pp

Publication Details

Published by CSIRO © 2009 all rights reserved. This work is copyright. Apart from any use as permitted under the Copyright Act 1968,

no part may be reproduced by any process without prior written permission from CSIRO.

ISSN 1835-095X

Cover photograph: Cloud covered Thornton Peak with sugarcane in foreground, N.E. Queensland

Courtesy of CSIRO Division Publishing

Photographer: CSIRO Publishing

© CSIRO 2009 August 2009 Water in the Northern Coral region ▪ iii

Director’s Foreword

Following the November 2006 Summit on the southern Murray-Darling Basin (MDB), the then Prime Minister and MDB

state Premiers commissioned CSIRO to undertake an assessment of sustainable yields of surface and groundwater

systems within the MDB. The project set an international benchmark for rigorous and detailed basin-scale assessment of

the anticipated impacts of climate change, catchment development and increasing groundwater extraction on the

availability and use of water resources.

On 26 March 2008, the Council of Australian Governments (COAG) agreed to expand the CSIRO assessments of

sustainable yield so that, for the first time, Australia would have a comprehensive scientific assessment of water yield in

all major water systems across the country. This would allow a consistent analytical framework for water policy decisions

across the nation. The Northern Australia Sustainable Yields Project, together with allied projects for Tasmania and

south-west Western Australia, will provide a nation-wide expansion of the assessments.

The CSIRO Northern Australia Sustainable Yields Project is providing critical information on current and likely future

water availability. This information will help governments, industry and communities consider the environmental, social

and economic aspects of the sustainable use and management of the precious water assets of northern Australia.

The projects are the first rigorous attempt for the regions to estimate the impacts of catchment development, changing

groundwater extraction, climate variability and anticipated climate change on water resources at a whole-of-region scale,

explicitly considering the connectivity of surface and groundwater systems. To do this, we are undertaking the most

comprehensive hydrological modelling ever attempted for the region, using rainfall-runoff models, groundwater recharge

models, river system models and groundwater models, and considering all upstream-downstream and surface-

subsurface connections.

To deliver on the projects CSIRO is drawing on the scientific leadership and technical expertise of national and state

government agencies in Queensland, Tasmania, the Northern Territory and Western Australia, as well as Australia’s

leading industry consultants. The projects are dependent on the cooperative participation of over 50 government and

private sector organisations. The projects have established a comprehensive but efficient process of internal and

external quality assurance on all the work performed and all the results delivered, including advice from senior academic,

industry and government experts.

The projects are led by the Water for a Healthy Country Flagship, a CSIRO-led research initiative established to deliver

the science required for sustainable management of water resources in Australia. By building the capacity and capability

required to deliver on this ambitious goal, the Flagship is ideally positioned to accept the challenge presented by this

complex integrative project.

CSIRO has given the Sustainable Yields Projects its highest priority. It is in that context that I am very pleased and proud

to commend this report to the Australian Government.

Dr Tom Hatton

Director, Water for a Healthy Country

National Research Flagships

CSIRO

iv ▪ Water in the Northern Coral region August 2009 © CSIRO 2009

Contributors to the Northern Australia Sustainable

Yields Project

Project director Tom Hatton

Sustainable Yields coordination Mac Kirby

Project Leader Richard Cresswell

Project Support Andrea Davis, Malcolm Hodgen, Sue Jackson, Helen Beringen, Justin Story, Siobhan Duffy, Therese

McGillion, Jeff Camkin

Data Management Mick Hartcher

Climate Tim McVicar, Randall Donohue, Janice Bathols, Francis Chiew, Dewi Kirono, Lingtao Li, Steve

Marvanek, David Post, Nick Potter, Ian Smith, Tom Van Neil, Wenju Cai

New South Wales Department of Water and Energy: Jin Teng

Catchment Yield Cuan Petheram, Paul Rustomji, Jamie Vleeshouwer, Donna Hughes, Jean-Michel Perraud, Ang Yang,

Lu Zhang

Sinclair Knight Merz: Brad Neal, Amanda Bell, Werner Hennecke, Damon Grace, Derek Goodin, Rory

Nathan, David Stephens, Nicola Logan, Sarah Gosling, Zuzanna Graszkiewicz

Queensland Department of Environment and Resource Management: Alex Loy, Greg Hausler, Sarah

Giles, David Li, Amanda Casey

Groundwater Glenn Harrington, Russell Crosbie, Phil Davies, James McCallum, Warrick Dawes, Matthew Lenahan,

David Rassam

Sinclair Knight Merz: Rick Evans, Roger Cranswick, Eliza Wiltshire

Jolly Consulting: Peter Jolly

Environmental Hydrology Associates: Peter Evans, Jerome Arunakumaren, Wesley Burrows, Judith

Raue

Northern Territory Department of Natural Resources, Environment, The Arts and Sport: Anthony

Knapton, Lynton Fritz, Steven Tickell

Queensland Department of Environment and Resource Management: Linda Foster, Ralph DeVoil

Environment Dave McJannet, Anne Henderson, Joe McMahon, Jim Wallace

Reporting Susan Cuddy, Becky Schmidt, Heinz Buettikofer, Elissa Churchward, Alex Dyce, Simon Gallant, Chris

Maguire, Frances Marston, Linda Merrin, Ben Wurcker

dmwcreative: Maureen Wicks, David Wicks

CSIRO unless otherwise indicated; Team Leaders underlined

© CSIRO 2009 August 2009 Water in the Northern Coral region ▪ v

Table of contents

NC-1 Water availability and demand in the Northern Coral region ......................................... 55 NC-1.1 Regional summary .........................................................................................................................................................56 NC-1.2 Water resource assessment ..........................................................................................................................................57 NC-1.3 Changes to flow regime at environmental assets ..........................................................................................................59 NC-1.4 Seasonality of water resources ......................................................................................................................................60 NC-1.5 Surface–groundwater interaction ...................................................................................................................................60 NC-1.6 Water storage options ....................................................................................................................................................61 NC-1.7 Data gaps.......................................................................................................................................................................61 NC-1.8 Knowledge gaps.............................................................................................................................................................61 NC-1.9 References.....................................................................................................................................................................62

NC-2 Contextual information for the Northern Coral region...................................................... 63 NC-2.1 Overview of the region ...................................................................................................................................................63 NC-2.2 Data availability ..............................................................................................................................................................74 NC-2.3 Hydrogeology .................................................................................................................................................................77 NC-2.4 Legislation, water plans and other arrangements ..........................................................................................................82 NC-2.5 References.....................................................................................................................................................................87

NC-3 Water balance results for the Northern Coral region........................................................ 88 NC-3.1 Climate ...........................................................................................................................................................................88 NC-3.2 WAVES potential diffuse recharge estimations..............................................................................................................95 NC-3.3 Conceptual groundwater models ...................................................................................................................................98 NC-3.4 Groundwater modelling results ......................................................................................................................................99 NC-3.5 Rainfall-runoff modelling results.....................................................................................................................................99 NC-3.6 River system water balance .........................................................................................................................................111 NC-3.7 Changes to flow regimes at environmental assets.......................................................................................................112 NC-3.8 References...................................................................................................................................................................116

vi ▪ Water in the Northern Coral region August 2009 © CSIRO 2009

Tables

Table NC-1. Estimated groundwater contribution (baseflow) to streamflow, modelled diffuse recharge and groundwater extraction for the Northern Coral region under historical climate .......................................................................................................................57 Table NC-2. List of Wetlands of National Significance located within the Northern Coral region......................................................68 Table NC-3. Estimated stock and domestic groundwater use and groundwater entitlements for the Northern Coral region............83 Table NC-4. Mean annual (water year), wet season and dry season rainfall and areal potential evapotranspiration averaged over the Northern Coral region under historical climate and Scenario C...................................................................................................92 Table NC-5. Recharge scaling factors in the Northern Coral region for scenarios A, B and C .........................................................95 Table NC-6. Summary results under the 45 Scenario C simulations (numbers show percentage change in mean annual rainfall and recharge under Scenario C relative to Scenario A) ....................................................................................................................97 Table NC-7. Summary results under the 45 Scenario C simulations for the modelled subcatchments in the Northern Coral region (numbers show percentage change in mean annual rainfall and runoff under Scenario C relative to Scenario A).........................107 Table NC-8. Water balance over the entire Northern Coral region under Scenario A and under scenarios B and C relative to Scenario A .......................................................................................................................................................................................109 Table NC-9. Standard metrics for changes to surface water flow regime at environmental assets in the Northern Coral region...113

Figures

Figure NC-1. Major rivers, towns and location of environmental assets selected for assessment of changes to hydrological regime in the Northern Coral region...............................................................................................................................................................55 Figure NC-2. Surface geology of the Northern Coral region with modelled mean dry season baseflow...........................................58 Figure NC-3. Spring groups and potential river baseflow in the Northern Coral region.....................................................................60 Figure NC-4. Surface geology of the Northern Coral region overlaid on a relative relief surface......................................................64 Figure NC-5. Historical (a) annual and (b) mean monthly rainfall averaged over the Northern Coral region. The low-frequency smoothed line in (a) indicates longer term variability .........................................................................................................................65 Figure NC-6. Map of current vegetation types across the Northern Coral region (source DEWR, 2005) .........................................66 Figure NC-7. Map of dominant land uses of the Northern Coral region (after BRS, 2002) ...............................................................67 Figure NC-8. False colour satellite image of Lloyd Bay (derived from ACRES, 2000). Clouds may be visible in image ..................69 Figure NC-9. False colour satellite image of the Lower Daintree River (derived from ACRES, 2000). Clouds may be visible in image .................................................................................................................................................................................................70 Figure NC-10. False colour satellite image of the Marina Plains – Lakefield Aggregation (derived from ACRES, 2000). Clouds may be visible in image .............................................................................................................................................................................71 Figure NC-11. False colour satellite image of the Newcastle Bay – Escape River Estuarine Complex (derived from ACRES, 2000). Clouds may be visible in image .........................................................................................................................................................72 Figure NC-12. False colour satellite image of Olive River (derived from ACRES, 2000). Clouds may be visible in image...............73 Figure NC-13. Location of streamflow gauging stations overlaid on a relative relief surface showing the proportion of gauges with flow above maximum gauged stage height across the Northern Coral region ..................................................................................75 Figure NC-14. Current groundwater monitoring bores in the Northern Coral region .........................................................................76 Figure NC-15. Groundwater salinity distribution for all bores drilled in the Northern Coral region ....................................................81 Figure NC-16. Groundwater management areas in the Northern Coral region .................................................................................84 Figure NC-17. (a) Historical annual rainfall and (b) its divergence from the long-term mean; and (c) historical annual areal potential evapotranspiration and (d) its divergence from the long-term mean averaged over the Northern Coral region................................89 Figure NC-18. Historical mean monthly (a) rainfall and (b) areal potential evapotranspiration and their temporal variation (range and ± one standard deviation) averaged over the Northern Coral region..........................................................................................89 Figure NC-19. Spatial distribution of historical mean annual (water year), wet season and dry season rainfall and areal potential evapotranspiration (potential evaporation) and their difference (rainfall less areal potential evapotranspiration ancross the Northern Coral region .......................................................................................................................................................................................90 Figure NC-20. Spatial distribution of (a) historical and (b) recent mean annual rainfall; and (c) their relative percent difference and (d) the statistical significance of these differences across the Northern Coral region .......................................................................91 Figure NC-21. Mean monthly (a) rainfall and (b) areal potential evapotranspiration averaged over the Northern Coral region under historical climate and Scenario C (C range is pooled from the 45 Scenario C simulations (15 global climate models and 3 global warming scenarios) – the lower and upper limits in C range are therefore not the same as scenarios Cdry and Cwet) ..................92 Figure NC-22. Spatial distribution of mean annual (water year), wet season and dry season rainfall across the Northern Coral region under historical climate and Scenario C .................................................................................................................................93 Figure NC-23. Spatial distribution of mean annual (water year), wet season and dry season areal potential evapotranspiration averaged over the Northern Coral region under historical climate and Scenario C...........................................................................94 Figure NC-24. Spatial distribution of historical mean recharge rate; and recharge scaling factors across the Northern Coral region for scenarios A, B and C ....................................................................................................................................................................96

© CSIRO 2009 August 2009 Water in the Northern Coral region ▪ vii

Figure NC-25. Percentage change in mean annual recharge under the 45 Scenario C simulations (15 global climate models and three global warming scenarios) relative to Scenario A recharge .....................................................................................................97 Figure NC-26 Map of the modelling subcatchments, calibration catchments and calibration gauging stations used for the Northern Coral region with inset highlighting (in red) the extent of the calibration catchments ......................................................................100 Figure NC-27. Modelled and observed monthly runoff and daily flow exceedance curve for each calibration catchment in the Northern Coral region. (Red text denotes catchments located outside the region; blue text denotes catchments used for streamflow modelling only).................................................................................................................................................................................103 Figure NC-28. Spatial distribution of mean annual (a) rainfall and (b) modelled runoff across the Northern Coral region under Scenario A .......................................................................................................................................................................................104 Figure NC-29. Mean annual (a) rainfall and (b) modelled runoff in the Northern Coral region under Scenario A ...........................104 Figure NC-30. Minimum, maximum and A range monthly (a) rainfall and (b) modelled runoff; and mean, median and A range monthly (c) rainfall and (d) modelled runoff in the Northern Coral region under Scenario A (A range is the 25th to 75th percentile monthly rainfall or runoff) .................................................................................................................................................................105 Figure NC-31. Spatial distribution of mean annual (a) rainfall and (b)modelled runoff across the Northern Coral region under Scenario B .......................................................................................................................................................................................106 Figure NC-32. Percentage change in mean annual runoff under the 45 Scenario C simulations (15 global climate models and three global warming scenarios) relative to Scenario A ............................................................................................................................107 Figure NC-33. Spatial distribution of mean annual rainfall and modelled runoff across the Northern Coral region under Scenario A and under Scenario C relative to Scenario A...................................................................................................................................108 Figure NC-34. Mean monthly (a) rainfall and (b) modelled runoff in the Northern Coral region under scenarios A and C. (C range is based on the consideration of each month separately – the lower and upper limits in C range are therefore not the same as scenarios Cdry and Cwet)................................................................................................................................................................109 Figure NC-35. Daily flow exceedance curves for (a) rainfall and (b) modelled runoff in the Northern Coral region under scenarios A, B and C. (C range is based on the consideration of each month separately – the lower and upper limits in C range are therefore not the same as scenarios Cdry and Cwet) .....................................................................................................................................110 Figure NC-36. Level of confidence in the modelling of runoff for (a) mid- to high flow events and (b) monthly dry season flow events for the modelling subcatchments of the Northern Coral region. 1 is the highest level of confidence, 5 is the lowest ..........111 Figure NC-37. Location of streamflow reporting nodes (guaging stations, environmental sites, dummy nodes and storage inflows) in the Northern Coral region.............................................................................................................................................................112

viii ▪ Water in the Northern Coral region August 2009 © CSIRO 2009

Abbreviations and acronyms

Abbreviation or acronym

Description

AHD Australian Height Datum

AMTD Adopted Middle Thread Distance (the distance along a river upstream from its outlet)

APET Areal potential evapotranspiration

AR4 The fourth assessment report of the Intergovernmental Panel on Climate Change

ARI Average recurrence interval – the statistical length of time that might be expected to pass before a similar condition is repeated

AWRC Australian Water Resources Council

BFI Baseflow index – the ratio of baseflow volume to total flow volume over a specified period, commonly assumed to be the amount of groundwater input to stream flow

BRS Bureau of Rural Sciences, Department of Agriculture, Fisheries and Forestry

CLW CSIRO Division of Land and Water

CMAR CSIRO Division of Marine and Atmospheric Research

CMB Chloride mass balance

CO2 Carbon dioxide

COAG Council of Australian Governments

CSIRO Commonwealth Scientific and Industrial Research Organisation

DEM Digital elevation model

DERM (Queensland) Department of Environment and Resource Management

DEWHA Department of the Environment, Water, Heritage and the Arts, Australian Government

DNRM Previous incantation of DERM

DNRW Previous incantation of DERM

DTW Depth to watertable

E Extraction

E/B Extraction to baseflow ratio

E/R Extraction to recharge ratio

Ef Future groundwater extraction

EC Electrical conductivity, a measure of salinity. 1 EC (S/cm) ≈ 0.6 mg/L TDS

ET Evapotranspiration

FDC Flow duration curve

GAB Great Artesian Basin

GCM Global climate model, also known as general circulation model

GDA Geographic datum of Australia

GDE Groundwater-dependent ecosystem

GRCI Groundwater resource condition indicator

IQQM Integrated Quantity and Quality Model – a river systems model

MAR Managed aquifer recharge

MDB Murray-Darling Basin

MGSH Maximum gauged stage height

MSLP Mean sea level pressure

NAILSMA Northern Australia Indigenous Land and Sea Management Alliance

NAS Network attached storage

NALWT Northern Australia Land and Water Taskforce (http://www.nalwt.gov.au/)

NAWFA Northern Australia Water Futures Assessment (http://www.environment.gov.au/nawfa/)

NRETA Previous incantation of NRETAS

NRETAS Northern Territory Department of Natural Resources, Environment, the Arts and Sport

NSE Nash-Sutcliffe Efficiency coefficient used to assess the predictive power of hydrological models. Values range from -∞ to +1, where +1 is a perfect match to observations. Analogous to the R2 coefficient of determination

PET Potential evapotranspiration

R Recharge

RAM Random access memory

RSF Recharge scaling factor

SAN Storage area network

© CSIRO 2009 August 2009 Water in the Northern Coral region ▪ ix

Abbreviation or acronym

Description

SILO Enhanced meteorological datasets (http://www.bom.gov.au/silo/index.shtml)

SRN Streamflow reporting node

TDS Total Dissolved Solids (mg/L ≈ 1.7 EC)

TRaCK Tropical Rivers and Coastal Knowledge Research Hub

WRON Water Resources Observation Network

Units of measurement

Measurement units Description

ML Megalitres, 1,000,000 litres

GL Gigalitres, 1,000,000,000 litres

TL Teralitres, 1,000,000,000,000 litres

Cumecs Cubic metres per second; m3/sec; equivalent to 1,000 litres per second

1 Sydney Harbour ~500 GL

1 Lake Argyle 10,380 GL

x ▪ Water in the Northern Coral region August 2009 © CSIRO 2009

Glossary of terms

Term Description

Scenarios Defined periods or conditions for comparative evaluation of water resource assessments. Each scenario has three variants: wet, mid and dry, representing the 90th, 50th and 10th percentile of ranked results for each modelled condition. These are referred to as the wet extreme, median and dry extreme variants for each scenario, A, B, C and D. Additional variants include: C range which represents the inter-quartile range of values (25-75% of values) and AN which represents the pre-development (i.e. near pristine) scenario based on Historical data. AN can be defined where river systems models are available

Historical Scenario A: 1st September, 1930 to 31st August, 2007 – except for recurrence interval calculation, when Historical refers to the period 1st September, 1930 to 31st August, 1996 (i.e. prior to Recent)

Recent Scenario B: 1st September, 1996 to 31st August, 2007

Future Scenario C: Climate conditions estimated for ~2030 compared to ~1990 conditions

Development The use of surface and groundwater supplies. This assessment assumes that all current entitlements are being fully used and, where possible, actual use is also considered. Future development assumes all entitlements projected to be made available in 2030 are fully utilised. This is referred to as Scenario D

Without development Scenarios AN, BN and CN. Represent conditions that would be expected under the climate scenarios without development, i.e. near-pristine conditions. These can be defined for systems with river systems models

Water Resource Assessment

An assessment that identifies the partitioning of rainfall through the water cycle, i.e. how much water there is in all its guises, at any given location, at any given time

Water Availability Assessment

An assessment that determines the amount of water that could be diverted or extracted from each water source, at any given location, at any given time

Water Sustainable Yield Assessment

An assessment that determines the amount of existing water resources that are available for consumptive use after the informed and equitable allocation of the resource between human uses and the environment

FCFC Forest Cover Flow Change (see <http://www.toolkit.net.au/Tools/FCFC>)

AWBM, Sacramento, SIMHYD, SMARG

Rainfall-runoff models (see http://www.toolkit.net.au/Tools/RRL)

IHACRES Classic IHACRES (Identification of unit Hydrographs And Component flows from Rainfall, Evaporation and Streamflow data) is a catchment-scale, rainfall-streamflow, modelling methodology that characterises the dynamic relationship between rainfall and streamflow, using rainfall and temperature (or potential evaporation) data, and predicts streamflow, developed by the Integrated Catchment Assessment and Management (iCAM) Centre, Faculty of Science, The Australian National University

MODFLOW A groundwater flow model (http://water.usgs.gov/nrp/gwsoftware/modflow.html)

WAVES An analytical recharge model developed by Zhang and Dawes (1998) used to estimate groundwater recharge under different soils, vegetation and climate scenarios

SRES 1B A future (2100) greenhouse gas emissions scenario used to compare climate model forecasts

Unallocated water Water that is identified as water potentially available for future allocation

General Reserve Unallocated water which may be granted for any purpose

Strategic Reserve Unallocated water which may only be granted for a state purpose

Water in the Northern Coral region

© CSIRO 2009 August 2009 Water in the Northern Coral region ▪ 55

NC

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NC-1 Water availability and demand in the Northern

Coral region

The first part of this report (the Preamble, Chapter 1 and Chapter 2) provides descriptions of climate and geology and the

methods that have been applied to this region and all regions of the Northern Australia Sustainable Yields study area. To

distinguish the study region from the drainage division, we refer to the region as the Northern Coral region (Figure NC-1).

This chapter summarises the water resources of the Northern Coral region, using information from Chapter NC-2

(Contextual Information) and Chapter NC-3 (Water Balance Results), and directly addresses the Terms of Reference,

specifically terms 3, 4 and 5 as listed in the Preamble. Essentially, this chapter provides a synoptic view of the region and

covers:

regional observations

water resource assessment

seasonality of water resources

surface–groundwater interaction

changes to flow regime at environmental assets

water storage options

data and knowledge gaps.

For further details on the context of the region (physical and climate descriptions, hydrogeology and legislation) see

Chapter NC-2. Region-specific methods and results are provided in Chapter NC-3. Modelling results are reported under

climate and development scenarios as defined at the division level in Section 2.1 of Chapter 2.

Figure NC-1. Major rivers, towns and location of environmental assets selected for assessment of changes to hydrological regime in the

Northern Coral region

56 ▪ Water in the Northern Coral region August 2009 © CSIRO 2009

NC

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NC-1.1 Regional summary

These regional observations summarise key modelling results and other relevant water resource information about the

Northern Coral region.

The Northern Coral region has a high inter-annual variability in rainfall and hence runoff and recharge. Coefficients of

variation are among the lowest of the regions across northern Australia, however, and the region may experience long

periods of many years that are considerably wetter or drier than others.

The mean annual rainfall for the region is 1338 mm. Mean annual areal potential evapotranspiration (APET) is 1853 mm.

The mean annual runoff averaged over the modelled area of the Northern Coral region is 373 mm, 28 percent of rainfall.

These values are amongst the highest in comparison to other regions across northern Australia. Under the historical

climate the mean annual streamflow over the Northern Coral region is estimated to be 17,364 GL.

There is a strong seasonality in rainfall patterns, with 92 percent of rain falling between November and May, and a very

high dry season (May to October) APET. The region has a relatively high rainfall intensity, and hence rapid runoff and

short lag between rainfall and runoff with a slightly increasing amount and intensity of rainfall over the historical (1930 to

2007) period.

There is a strong north–south and east–west rainfall gradient and between 10 and possibly greater than 50 percent of

precipitation flows as runoff.

Annually, as APET is greater than rainfall, the region can be described as being water-limited – in other words there is

more energy available to remove water than there is water available to be removed. The far south-east, however,

receives more rain than can be evaporated throughout the year. Most of the region has a rainfall surplus through the wet

season (November to April).

The Northern Coral region has a recent (1996 to 2007) climate record that is statistically significantly slightly wetter than

the historical record. Rainfall was 8 percent higher; runoff was 19 percent higher. It is likely that future (~2030) conditions

will be similar to historical conditions; hence, future runoff and recharge will also be similar to historical levels, and lower

than the recent past.

Most groundwater use is sourced from the Gilbert River Formation of the Great Artesian Basin, which occurs extensively

in outcrop in the region. Younger, shallow aquifers do not provide a viable groundwater resource in this region, due to

variable thickness and groundwater quality and because these aquifers can empty during the dry season. Groundwater

is, however, an important source of baseflow to a number of rivers in this region. Groundwater extraction volumes are

negligible, relative to the volume of baseflow to rivers, and hence are not likely to significantly impact dry season

streamflows.

At environmental assets surface water flows are highly dominated by wet season flows so dry season flows are only a

small fraction of total annual flow. However, environmental assets are adapted to this strong seasonality and any

significant changes in the frequency and duration of wet season high flows and dry season low flows are likely to have an

environmental impact.

In the recent past there has been significantly more flow at most environmental assets. Annual and seasonal flows do not

change much under the median future climate; hence there is little change in the high and low flow threshold exceedance

under this scenario. There are large changes to the high flow threshold exceedance under the wet and dry extreme

future climates which could have negative environmental impacts. There is little chance that streamflow will cease in any

year under the given scenarios.

The region is generally datapoor.


NC

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NC-1.2 Water resource assessment

NC-1.2.1 Under historical climate and current development

The mean annual rainfall and runoff averaged over the Northern Coral region are 1388 mm and 373 mm respectively.

These values fall in the upper end of the range of values from the 13 regions. The coefficient of variation of annual

rainfall and modelled runoff averaged over the Northern Coral region are 0.27 and 0.49. These values are among the

lowest of the 13 regions. The 10th percentile, median and 90th percentile annual modelled runoff values across the

Northern Coral region are 616, 348 and 159 mm respectively.

Under a continuation of the historical climate, mean annual diffuse groundwater recharge to unconfined aquifers of the

Northern Coral region is likely to be similar to the historical (1930 to 2007) average rate. Current groundwater extraction

is estimated to be 13.5 GL/year (Table NC-1). Because this is very small compared with the historical rate of diffuse

recharge, continued extraction at this rate under a historical climate would be unlikely to cause widespread declines in

groundwater levels. Nevertheless, where existing groundwater developments are located near any of the major perennial

rivers, continued extraction may ultimately impact on streamflow in the rivers by reducing baseflow contributions (Table

NC-1 and Figure NC-2).

Table NC-1. Estimated groundwater contribution (baseflow) to streamflow, modelled diffuse recharge and groundwater extraction for the

Northern Coral region under historical climate

Station River Station name Annual BFI * Dry season BFI *

Dry season baseflow *

GL

102101A Pascoe Fall Ck 0.25 0.60 20.7

104001A Stewart Telegraph Rd 0.16 0.53 2.0

105001A Hann Kalinga Homestead 0.30 0.74 7.9

105101A Normanby Battle Camp 0.18 0.51 10.8

105102A Laura Coalseam Ck 0.09 0.38 0.8

105103A Kennedy Fairlight 0.15 0.48 2.7

105105A East Normanby Developmental Rd 0.20 0.57 5.1

107001A Endeavour Flaggy 0.24 0.53 6. 6

107002A Annan Mount Simon 0.29 0.56 31.5

108002A Daintree Bairds 0.39 0.67 122.4

109001A Mossman Mossman 0.38 0.57 45.1

Historical recharge ** Estimated groundwater extraction

GL/y

Entire Northern Coral region 12,340 13.5

* BFI (baseflow index) and baseflow volume derived from gauged data. ** Aggregated modelled recharge from Zhang and Dawes (1998)

Term of Reference 3a

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Figure NC-2. Surface geology of the Northern Coral region with modelled mean dry season baseflow

NC-1.2.2 Under recent climate and current development

The mean annual rainfall and modelled runoff under the recent (1996 to 2007) climate are 8 percent and 19 percent

higher respectively than the historical mean values.

Under a recent climate, mean annual diffuse groundwater recharge is likely to remain similar to the historical average

rate for the entire region. However, there are likely to be different areas in both the north and south of the Northern Coral

region where recharge could be expected to be higher or lower on average than the historical value.

NC-1.2.3 Under future climate and current development

Rainfall-runoff modelling with climate change projections from nine of the global climate models (GCMs) shows an

increase in mean annual runoff, while rainfall-runoff modelling with climate change projections from six of the GCMs

shows a decrease in mean annual runoff. Under the high global warming scenario, rainfall-runoff modelling with climate

change projections from two of the GCMs indicates a decrease in mean annual runoff greater than 10 percent while

Term of Reference 3a (ii)

Term of Reference 3a (iii)


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rainfall-runoff modelling with climate change projections from two of the GCMs indicates an increase in mean annual

runoff greater than 10 percent. Under the historical climate, the wet extreme, median and dry extreme scenarios mean

annual modelled runoff increases by 36 and 1 percent and decreases by 19 percent relative to Scenario A. By

comparison, the range based on the low global warming scenario is a 19 to -11 percent change in mean annual modelled

runoff.

Under the future climate, mean annual diffuse groundwater recharge is likely to be on average higher than the historical

mean value. Some parts in the south of the region are however likely to experience a decline in mean annual recharge.

The impacts of future groundwater extraction at current rates will therefore be varied; groundwater levels and fluxes in

the south may decline, while in the centre and north of the region groundwater levels and fluxes may increase. The

impacts of extraction on dry season baseflow contributions to perennial rivers will depend on the proximity of the

extraction bore to the rivers, and could be significant in the south of the region.

NC-1.2.4 Under future climate and future development

No future development scenarios were considered for this region.

NC-1.3 Changes to flow regime at environmental

assets

Section 1.3 of the division-level Chapter 1 describes how environmental assets were shortlisted for assessment by this

project. Five environmental assets were shortlisted for the Northern Coral region: Lloyd Bay, Lower Daintree River,

Marina Plains – Lakefield Aggregation, Newcastle Bay – Escape River Estuarine Complex, and Olive River. These

assets are characterised in Chapter NC-2.

In deciding whether it is feasible to report hydrological regime metrics for these shortlisted assets, it is important to

consider the confidence levels in modelled streamflow (as described in Section 2.2.6 of the division-level Chapter 2).

Confidence in results for low flows and high flows was calculated separately. Hydrological regime metrics (as defined in

Section 2.5 of the division-level Chapter 2) for either low flows or high flows are reported only where confidence levels

are sufficiently high. If confidence in the low flow or high flow is too low, metrics are not reported, and hence an important

gap in our knowledge is identified.

Some of the assets in this region have multiple nodes at which streamflow modelling results are available. When

reporting hydrological regime metrics for such assets a single node was selected. The selected node was that with the

highest streamflow confidence level and the largest proportion of streamflow to the asset. The locations of nodes for

each asset are shown on satellite images in Section NC-2.1.3. Results for all nodes are presented in McJannet et al.

(2009).

The confidence levels in modelled streamflow are sufficiently high to report a full set of hydrological regime metrics at

three assets in this region. At two of the assets, Lloyd Bay and Olive River, confidence in the low flow metrics was

considered unreliable and these metrics are therefore not reported. The surface water flow confidence level for the

Newcastle Bay – Escape River Estuarine Complex is considered unreliable for high flows so metrics relating to such

flows are also not reported.

Annual flow into all assets is dominated by wet season flow, which has been as much as 29 percent higher under the

recent climate. Dry season flows have been significantly higher (up to 30 percent) under the recent climate.

Under the future climate, flows are expected to be similar to the historical record, though the wet extreme future climate

may see significant increases, while the dry extreme future climate may see moderate decreases.

The number of days when flow is below the low flow threshold is projected to be similar under both the historical and

future climates. Zero flow days do not occur and this is unlikely to change. Where we have confidence in the data (Lower

Daintree River, and Marina Plains – Lakefield Aggregation) there is little change expected under future climate when

compared to historical levels.

Term of Reference 3a (iv)

Term of Reference 3b


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NC-1.4 Seasonality of water resources

Approximately 92 percent of rainfall and 89 percent of modelled runoff occurred during the wet season months under the

historical climate. Under recent climate 93 percent of rainfall and 89 percent of runoff occurred during the wet season

months. Under future climate it is estimated that 93 percent of rainfall and 90 percent of runoff will occur during the wet

season months. Runoff is highest in February and March.

NC-1.5 Surface–groundwater interaction

Groundwater is critical for maintaining river flow into the dry season in many catchments in the Northern Coral region.

The rivers identified by DNRM (2005) as potentially receiving groundwater inflow from the Gilbert River Formation and

Dalrymple sandstone aquifers include the Normanby, Laura, Little Laura, Hann, Olive, Pascoe, Kennedy and Marrett

(Figure NC-3). Of these rivers however, only the Hann River maintains flow through the entire dry season. In the Bathurst

Heads – Cape Melville National Park area, spring discharges also support wetlands and swamps.

During the wet season, water infiltrates from rivers to alluvial sediments (where present) either laterally via the incised

sediments, or vertically via diffuse flood-out recharge when overbank flooding occurs.

Figure NC-3. Spring groups and potential river baseflow in the Northern Coral region

Term of Reference 4

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NC-1.6 Water storage options

NC-1.6.1 Surface water storages

There are no large storages in the Northern Coral region.

NC-1.6.2 Groundwater storages

Due to the high annual rainfall in this region, groundwater recharge rates are significantly higher than almost all other

regions within the project area. Accordingly, most near-surface aquifers are completely replenished each wet season,

including those resources currently being developed. Therefore managed aquifer recharge (MAR) has limited prospects

in this region, simply because there is no additional storage capacity within the aquifers at the end of each wet season.

NC-1.7 Data gaps

Time series groundwater level and salinity data is required for each of the main aquifer types in the Northern Coral region

to provide greater understanding of recharge processes, surface-groundwater interaction and inter-aquifer leakage,

particularly for the Great Artesian Basin aquifers.

NC-1.8 Knowledge gaps

Diffuse upward leakage of water out of the Great Artesian Basin aquifers and into overlying Cainozoic sediments is yet to

be quantified. Further research is required to estimate these discharge fluxes so that a detailed groundwater balance can

be developed for the aquifers to guide future management in the region.

1. None of the environmental assets in this region have any site specific metrics by which to gauge the potential

impacts of future climate change and development scenarios. In the absence of site specific metrics a set of

standard metrics related to high and low flows have been utilised; however, the conversion of these metrics into

environmental impacts still requires development of quantitative relationships between flow and specific ecological

entities (for example, macrophyte populations, fish passage, faunal and floral habitats, etc.).

2. Flooding is an important factor that sustains many environmental assets and this occurs when the stream breaks

out of its banks (a level known as bankfull stage or discharge). However, bankfull discharge is not known for many

streams, nor is the dependence of area flooded on increasing stream depth, so it is difficult to predict when assets

are inundated. Further information about bankfull stage and discharge are needed for most environmental assets.

3. Dry season flows are poorly understood in this region - therefore the ability to predict the potential impacts of the

various scenarios on low or zero flows at environmental assets is very limited. Improved monitoring of low

streamflow conditions is needed along with the development of hydrological models that combine surface and

groundwater regimes. Further monitoring of groundwater levels is also required so that the potential impacts of

climate change and development scenarios on groundwater dependant ecosystems can be better understood.

4. Many environmental assets depend not simply on duration above or below certain flow levels, but on triggers (e.g.

for reproduction or migration) set by the rate of change of flow. In addition, some environmental assets depend on

the frequency and duration of events that occur less than annually (i.e. once every 5, 10 or 20 years or more).

Further analysis is therefore required to look at how the timing, duration and rate of rise and fall in flow rates at

critical times of the season will vary under the various scenarios.

Term of Reference 5

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NC-1.9 References

DNRM (2005) Hydrogeological framework report for the Great Artesian Basin resource plan area. Queensland Department of Natural Resources and Mines, Brisbane.

McJannet DL, Wallace JW, Henderson A and McMahon J (2009) High and low flow regime changes at environmental assets across northern Australia under future climate and development scenarios. A report to the Australian Government from the CSIRO Northern Australian Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, Australia. In prep.

Zhang L and Dawes WE (1998) WAVES – an integrated energy and water balance model. CSIRO Land and Water Technical Report No 31/98.


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NC-2 Contextual information for the Northern Coral

region

This chapter summarises the background information for the region, outlining existing knowledge of water resources and

prior and current investigations relevant to the water resources of the region. This chapter also outlines the current and

potential future legislation, water plans and other water resource management arrangements. This chapter is arranged

into four sections:

physical and climate descriptions

data availability

hydrogeology

legislation, water plans and other arrangements.

NC-2.1 Overview of the region

NC-2.1.1 Geography and geology

The Northern Coral region extends from the tip of Cape York, along the eastern flank of the Great Dividing Range to Port

Douglas in the south. The region comprises 9 river basins. From north to south these are: Jacky Jacky Creek, Olive –

Pascoe rivers, Lockhart River, Stewart River, Normanby River, Jeannie River, Endeavour River, Daintree River and

Mossman River. The region covers nearly 47,000 km2, and most of the rivers flow east to west, originating in the Great

Divide and flowing through extensive floodplains. The east coast waterways are relatively short with small catchments

due to the close proximity of the mountain ranges. Eastern wetlands are extensive but with few lagoons. Artesian springs

associated with the Great Artesian Basin are also evident, particularly at the northern tip of the bioregion. The coast has

recently formed dune fields and beach ridges, which are extensive in Cape Bedford/Cape Flattery near Cooktown, and

the Olive River.

The northerly trending high ranges and plateaux rise up to 800 m and are flanked by foothills and broad low-relief plains.

Extensive alluvial fans have developed in the lower reaches of many of the main river systems, such as the Normanby

River into Prince Charlotte Bay.

The region consists of a complex geology dominated by the Torres Strait Volcanics in the north. The Proterozoic (545 to

1600 million years old) metamorphic rocks and Devonian (354 to 410 million years old) acid intrusive rocks of various

ages of the Coen-Yambo Inlier run north to south along the eastern margin of the region and encompass the high altitude,

high rainfall areas of Iron Range and McIlwraith Range. The deeply dissected sandstone plateaus and ranges of the

Battle Camp Sandstones lie in the south of the region adjacent to the undulating Laura Lowlands composed of residual

weathered sands and flat plains of colluvial and alluvial clays, silts and sands (Bain and Draper, 1997).


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Figure NC-4. Surface geology of the Northern Coral region overlaid on a relative relief surface

NC-2.1.2 Climate, vegetation and land use

The Northern Coral region receives an average of 1338 mm of rainfall over the September to August water year, most of

which (1233 mm) falls in the November to April wet season (Figure NC-5). Annual rainfall is highest along the coast,

ranging between 3640 mm in the south-east and 917 mm further inland. Over the historical (1930 to 2007) period, annual

rainfall has been gradually increasing from an initial average of around 1250 mm to approximately 1400 mm later in the

period. The highest regional average yearly rainfall received was 2143 mm which fell in 1974, and the lowest was

769 mm in 1961.

Areal potential evapotranspiration (APET) is very high across the region, averaging 1853 mm over a water year, and

varies little across the seasons. APET generally remains higher than rainfall for most of the year resulting in near-year-

round water-limited conditions. The exceptions to this are the months of January to March, when more rain falls than can

potentially be evaporated.


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Figure NC-5. Historical (a) annual and (b) mean monthly rainfall averaged over the Northern Coral region. The low-frequency smoothed

line in (a) indicates longer term variability

The most extensive vegetation types are predominantly Darwin Stringybark (Eucalyptus tetrodonta) woodlands, usually

in association with bloodwoods Corymbia nesophila, C. hylandii or C. clarksoniana, and Melaleuca viridiflora low open-

woodlands. Other extensive vegetation types include Corymbia clarksoniana, Eucalyptus chlorophylla and E. cullenii

woodlands, grasslands and grassy open-woodlands, heathlands, and sedgelands, and notophyll vine forests, with semi-

deciduous mesophyll vine forests on the eastern ranges and deciduous vine thickets on drier western slopes. Extensive

mangrove forests are found in Kennedy Inlet in the north-east of the region and in estuaries. Rainforests are associated

with the wetter areas along the east coast ranges. A total of 3338 species of plants have been recorded in the region with

the most common being grasses and sedges. Of these, 379 are rare and threatened and 247 are naturalised exotics.

Endangered species found in the region include a fern (Cyathea exilis), orchids (Dendrobium antennatum, Dendrobium

mirbelianum), Dipodium pictum, Eremochloa muricata, Habenaria macraithii, Huperzia carinata, Muellerargia timorensis,

and Phalaenopsis rosenstromii (Sattler & Williams, 1999).


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Figure NC-6. Map of current vegetation types across the Northern Coral region (source DEWR, 2005)

Land uses include broad acre pastoralism, silica sand mining, nature reserves, tourism and fishing (Sattler & Williams,

1999). Land within the region has been dedicated to national parks and to Aboriginal and Torres Strait Islander use.

Pastoral leased land occupies about half of the total area, Aboriginal people oversee about 20 percent, and National

Parks manages about 10 percent. Most of the pastoral leases occupy the centre of the region and across to locations on

the east coast. Lakefield National Park is a major national park in the south-east of the region.

A very small portion of land has been cleared in the Northern Coral region. It is dominated by dune fields, rainforests,

wild rivers and wetlands. There are currently three mines in operation in the region and these are:

the Cape Flattery silica mine

the Norton gold mine

the Collingwood tin mine.


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Figure NC-7. Map of dominant land uses of the Northern Coral region (after BRS, 2002)


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NC-2.1.3 Regional environmental asset description

Environmental assets were chosen from wetlands which are listed in the Directory of Important Wetlands in Australia

(Environment Australia, 2001). From this directory, environmental assets were shortlisted for assessing changes to the

hydrological regime under the climate and development scenarios. The selection of this shortlist was undertaken in

consultation with state governments and the Australian Government through direct discussions and through internal

reviews (see Section 1.3 in the division-level Chapter 1 for further detail).

All nationally, or internationally, important wetlands listed for the Northern Coral region in the Directory of Important

Wetlands in Australia (Environment Australia, 2001) are detailed in Table NC-2, with asterisks identifying the five

shortlisted assets: Lloyd Bay, Lower Daintree River, Marina Plains – Lakefield Aggregation, Newcastle Bay – Escape

River Estuarine Complex and Olive River. The location of these shortlisted wetlands is shown in Figure NC-1. There are

no wetlands classified as Ramsar sites in this region. Wetlands may be nationally or regionally significant depending on

more locally specific criteria. All wetlands are important for a variety of ecological reasons or because they bear historical

significance or have high cultural value, particularly to Indigenous people.

The following section characterises these shortlisted wetlands and is based largely on the description of these assets as

outlined by Environment Australia (2001). Chapter NC-3 presents the assessment of those shortlisted assets, and

reports hydrological regime metrics for those assets which have sufficient confidence in the modelled streamflow to

enable analysis.

Table NC-2. List of Wetlands of National Significance located within the Northern Coral region

Site code Name Area Ramsar site

ha

QLD137 Alexandra Bay 862 No

QLD059 Cape Flattery Dune Lakes 44,000 No

QLD060 Cape Grenville Area 7,310 No

QLD061 Cape Melville - Bathurst Bay 5,460 No

QLD062 Harmer Creek - Shelburne Bay Aggregation 31,300 No

QLD147 Hilda Creek Headwater <10 No

QLD090 Laura Sandstone 1,090 No

QLD064 * Lloyd Bay 15,700 No

QLD154 * Lower Daintree River 5,270 No

QLD065 * Marina Plains - Lakefield Aggregation 392,000 No

QLD066 * Newcastle Bay - Escape River Estuarine Complex 42,300 No

QLD069 * Olive River 17,600 No

QLD070 Orford Bay - Sharp Point Dunefield Aggregation 17,100 No

QLD072 Princess Charlotte Bay Marine Area 87,700 No

QLD073 Silver Plains - Nesbitt River Aggregation 44,800 No

QLD076 Temple Bay 4,400 No

QLD077 The Jack Lakes Aggregation 35,000 No

QLD078 Violet Vale 1,890 No

* Asterisk against the site code identifies those shortlisted for assessment of changes to hydrological regime.


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Lloyd Bay

The heath and closed forest communities that dominate the Lloyd Bay area (Figure NC-8) are regionally rare and are

amongst the best examples of these communities on Cape York Peninsula. The area also supports seagrass beds that

are outstanding for their size and diversity (Abrahams et al., 1995). These seagrass beds are important Dugong habitat.

The site has an area of 15,700 ha and an elevation between zero and 5 m above sea level (Environment Australia, 2001).

Figure NC-8. False colour satellite image of Lloyd Bay (derived from ACRES, 2000). Clouds may

be visible in image

The major vegetation type on the site is heath. A significant area of evergreen notophyll vine forest is also present. Salt

flats are relatively extensive, occurring on the landward side of the mangroves. These are almost devoid of vegetation

(Environment Australia, 2001). Numerous swamps and dune lakes occur in the area. The site has some Indigenous and

European cultural significance.


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Lower Daintree River

The Lower Daintree River (Figure NC-9) site contains a well defined array of geomorphological features that are

representative of coastal expansion within a confined space. The tall closed red mangrove forest that lines the mid tidal

reaches of the site is an outstanding example of the type. The paperbark swamps of the northern bank are an

outstanding and spectacular example of this type of forest. These swamps may also be the most significant breeding

area for the saltwater crocodile in the Wet Tropics bioregion. The site has an area of 5270 ha and an elevation less than

10 m above sea level (Environment Australia, 2001).

Fourteen vegetation types have been distinguished in the area, including mangrove communities, melaleuca

communities, rainforest communities, dune woodlands and thickets, and sedge lands (Environment Australia, 2001).

Much of the Daintree floodplain has been cleared for cane production or grazing. Some areas have been cleared to the

water’s edge, and bank erosion in some areas is severe (Environment Australia, 2001).

Figure NC-9. False colour satellite image of the Lower Daintree River (derived from ACRES, 2000).

Clouds may be visible in image


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Marina Plains – Lakefield Aggregation

The Marina Plains – Lakefield Aggregation site (Figure NC-10) is located to the south of Princess Charlotte Bay. It is

characterised by inland wetlands including permanent rivers, streams and ponds, seasonally inundated areas and

floodplains. Most of the site is inundated during the wet season. The site has an area of 392,000 ha and an elevation

between zero and 100 m above sea level (Environment Australia, 2001).

Figure NC-10. False colour satellite image of the Marina Plains – Lakefield Aggregation (derived

from ACRES, 2000). Clouds may be visible in image

There are a very large number of ephemeral lakes and lagoons and these are occupied by many species of aquatic

plants. This site contains some of the best examples of many vegetation communities on the eastern side of Cape York

Peninsula and is a significant habitat for saltwater crocodiles (Environment Australia, 2001).


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Newcastle Bay – Escape River Estuarine Complex

The Newcastle Bay – Escape River Estuarine Complex site (Figure NC-11) is characterised by both marine and coastal

zone wetlands and inland wetlands including estuarine areas, permanent and seasonal brackish swamps, mud flats, tidal

marshes and swamp forests. This site has an area of 42,300 ha and an elevation ranging between zero and 30 m above

sea level, although the majority is less than 5 m (Environment Australia, 2001).

Figure NC-11. False colour satellite image of the Newcastle Bay – Escape River Estuarine Complex

(derived from ACRES, 2000). Clouds may be visible in image

This is a large, shallow, sheltered estuarine complex with low gradient foreshores composed of recent sediments that

have been colonised by mangroves (Environment Australia, 2001). A distinctive feature is the relative rarity of salt flats in

the marine-terrestrial transition area. There are about 2000 ha of salt flats on the site but most of them are located in the

middle of mangrove islands. Most of the brackish and freshwater wetlands on the site margins are occupied by

sedgeland (Neldner and Clarkson, 1995). Shallow banks of seagrass occur in the Escape River and the site includes

some of the best examples of closed red mangrove forest on Cape York Peninsula (Environment Australia, 2001).

The area is traditional Indigenous land. The area also has European historical significance as it is where the tragic

Kennedy expedition ended in 1848. Both Kennedy Inlet and the Escape River are listed as estuaries of high fisheries

importance (Bucher and Saenger, 1989).


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Olive River

Nearly all of the catchment area of the Olive River site (Figure NC-12) is of high or very high wilderness quality. The

vegetation of the area is very diverse. Soil quality and drainage characteristics vary significantly over short distances and

combine to form a very complex and significant vegetation mosaic. Fish diversity is exceptionally high for an Australian

river of this size and is of biogeographic significance (Herbert et al., 1994). The site has an area of 17,600 ha and an

elevation between zero and 40 m above sea level (Environment Australia, 2001).

Figure NC-12. False colour satellite image of Olive River (derived from ACRES, 2000). Clouds may

be visible in image

.

The site supports seagrass meadows, communities of mangroves, sedgelands, paperbark forests and aquatic plants.

Evergreen mesophyll/notophyll vine forest grows in frequently inundated dune swales near the mouth of the river. The

banks of the Olive River support some of the best examples of evergreen mesophyll riparian vine forest on Cape York

Peninsula (Environment Australia, 2001). The site is one of three outstanding saltwater crocodile habitat areas on the

Cape York Peninsula (Taplin, 1987). Significant winter concentrations of migrating waders occur in swamps associated

with the river (Le Cussan, 1993).


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NC-2.2 Data availability

NC-2.2.1 Climate

The rainfall-runoff modelling uses historical daily climate data (Scenario A) from the SILO database for the period

1 September 1930 to 31 August 2007 at 0.05 x 0.05 degree (~ 5 x 5 km) grid cells. Full details and characterisation of

the SILO database are provided at the division level in Section 2.1 of Chapter 2. Scenario B and Scenario C climate data

are rescaled versions of the Scenario A data; this is also discussed in Section 2.1 of Chapter 2.

NC-2.2.2 Surface water

Streamflow gauging stations are or have been located at 28 locations within the Northern Coral region. Seven of these

gauging stations are either: flood warning stations and measure stage height only, or have less than ten years of

measured data. Of the remaining 21 stations, 14 recorded more than half of their total volume of flow during events that

exceed their maximum gauged stage height. In the Northern Coral region hydraulic modelling methods have been used

to derive rating curves at some stations because the stations are remote and inaccessible during the wet season.

However the use of hydraulic modelling methods in some parts of the Northern Coral region is problematic due to the

steep river gradients, which lead to high river flow velocities. High river flow velocities amplify errors when using these

methods. Figure NC-13 shows the spatial distribution of data of acceptable quality (duration) and the percentage of flow

above maximum gauged stage height (MGSH) (this assessment was only undertaken on stations with ten years or more

data). The majority of gauging stations in the Northern Coral are located in the southern half of the region. The small

catchments to the north are largely inaccessible. There are 15 gauging stations currently operating in the Northern Coral

region at a density of one gauge for every 3100 km2. For the 13 regions the median number of current gauging stations

per region is 12 and the median density of current gauging stations per region is one gauge for every 9700 km2. Although

the Northern Coral region has a high density of current gauging stations relative to the other 12 regions in northern

Australia, the density is low relative to the Murray-Darling Basin average. (The mean density of current stream gauging

stations across the entire Murray-Darling Basin is one gauge for every 1,300 km2.)


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Figure NC-13. Location of streamflow gauging stations overlaid on a relative relief surface showing the proportion of gauges with flow

above maximum gauged stage height across the Northern Coral region

NC-2.2.3 Groundwater

The Northern Coral region contains a total 1274 registered groundwater bores. Of these, 601 bores have surveyed

elevations that could enable watertable surfaces to be constructed for the main aquifers. However these bores are not

necessarily monitored on a regular basis. There are 25 water level monitoring bores in the region; two are historical and

23 are current (Figure NC-14). All of the 23 current monitoring bores are for sub-artesian aquifers.


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Figure NC-14. Current groundwater monitoring bores in the Northern Coral region

NC-2.2.4 Data gaps

Time series groundwater level and salinity data are required for each of the main aquifer types in the Northern Coral

region to provide greater understanding of recharge processes, surface-groundwater interaction and inter-aquifer

leakage, particularly for the Great Artesian Basin aquifers.


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NC-2.3 Hydrogeology

This section describes the key sources of groundwater in the Northern Coral region.

NC-2.3.1 Aquifer types

The Northern Coral region comprises a number of different tectonic units; from north to south these include the

Carpentaria Basin, the Coen Inlier, the Laura Basin and the Hodgkinson Province. There are essentially three main

aquifer types in the region associated with these units: fractured basement rocks, sedimentary GAB aquifers and

unconsolidated Cainozoic sediments.

Fractured rock aquifers of the Coen Inlier and Hodgkinson Province

The Hodgkinson Province exists south of the Laura Basin while the Coen Inlier resides to the north of it. Together these

tectonic units comprise the fractured rock aquifers in this region. The Lower Palaeozoic Coen Inlier comprises

metamorphic and predominantly Permian intrusive rocks. The Devonian to Permian Hodgkinson Province consists of

deep water siltstones, arenites, conglomerates and basalts. Both fractured rock units have experienced tectonic

compression and metamorphism (Horn et al., 1995). These fractured rock aquifers derive their groundwater storage

capability from secondary porosity features such as joints, faults and voids. Aquifer yields are generally low, however,

are also highly variable depending on the character of fractures intersected when drilling.

Groundwater bores constructed in the intrusive rocks of the Coen Inlier are typically less than 25 m deep. Below this

depth the granite becomes massive, with negligible groundwater storage capacity. The primary source of groundwater is

contained within the weathered zones of the granite (Horn et al., 1995).

Groundwater yields from the Hodgkinson Province range from 0.5 to 30 L/second and average 5 L/second. Groundwater

supplies are usually obtained from relatively shallow depths of less than 60 m; below this depth bedding surfaces and

cleavage partings are typically closed and there is a significant reduction in porosity and permeability (AGE, 2007).

Great Artesian Basin aquifers

Groundwater resources in porous consolidated rocks are essentially restricted to the Great Artesian Basin (GAB) in the

Northern Coral region. The GAB consists of alternating layers of water bearing sandstone aquifers and non-water

bearing siltstones and mudstone aquitards. This confined aquifer system was deposited throughout the Triassic, Jurassic

and Cretaceous periods.

The Orford Bay and Cape Weymouth 1:250 000 geological map sheets (Willmott et al., 1976; Willmott and Powell, 1977)

show that the GAB aquifers are continuous over the Great Dividing Range. Thus the western boundary of the Northern

Coral region does not coincide with a groundwater divide, at least for this aquifer system.

The GAB comprises a number of sedimentary basins. A small portion of the Carpentaria Basin and the entire Laura

Basin is incorporated in the Northern Coral region, separated by the Coen Inlier. The geological evolution of the Laura

Basin correlates with that of the Carpentaria Basin and the sedimentary sequences are of similar age and nature. The

Laura Basin is connected with the Carpentaria Basin over the Kimber Arch. The groundwater resources of the GAB

aquifers within these two basins are described together herein.

The Dalrymple Sandstone and the Gilbert River Formation span the entire Laura Basin and contain the most significant

aquifer systems. They are the shallowest major artesian aquifers and the most frequently intercepted by water bores in

the GAB in Queensland (DNRM, 2005). An equivalent of the Gilbert River Formation exists in the Carpentaria Basin in

this region, called the Helby Beds. They differ from the equivalent formation to the south in that the aquifers are

unconfined over most of the onshore occurrence. These beds have a thickness of approximately 300 m and have the

potential to provide useful supplies of good quality water (DNRM, 2005). The Helby Beds shall be considered as the

Gilbert River Formation herein. The Gilbert River Formation consists of fluvial and marginal marine sediments. In the

Laura Basin, it ranges in thickness from 60 m in the east to over 200 m in the central part of the basin (Horn et al., 1995).


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The Dalrymple Sandstone is predominantly composed of fluvial/deltaic sediments and is the basal Mesozoic unit in the

Laura Basin (Horn et al., 1995). This formation varies in thickness from approximately 60 m near the outcrop in the

eastern part of the basin to over 500 m near the coast. These sandstones occupy a significant area of surface outcrop in

the east of the region north of Cooktown. The aquifers of the Gilbert River Formation and the Dalrymple Sandstone are

similar and in some cases indistinguishable. Furthermore, the Dalrymple Sandstone is considered hydraulically

connected to the Gilbert River Formation (DNRM, 2005) and will be considered an equivalent from this point forward.

In the Laura Basin the thickness of the combined Gilbert River and Dalrymple Sandstone Formations range up to 700 m

in the central part of the basin (Horn et al., 1995). Groundwater yields are variable (from 2 to 15 L/second) as aquifer

transmissivity is largely controlled by fracture density and faulting rather than the primary porosity of the rock itself

(DNRM, 2005). Measurement of specific aquifer parameters has only been attempted in one small area of the Laura

Basin, the Bathurst Range coal prospect (Horn et al., 1995). Transmissivities range from 5 to 1000 m2/day and the

storage coefficient ranges from 2 X 10-3 to 4 X 10-1. The water levels in the unconfined parts of the Bathurst Range are

from zero to 30 m below ground level (mBGL) whilst where aquifers are confined the range is from zero to 6.5 m above

ground level (mAGL). In the southern Laura Basin the unconfined water levels range from 60 to 80 mBGL and in the

confined areas, range from zero to 10 mAGL.

The Rolling Downs Group is a lower permeability unit, typically considered as a confining layer to the Gilbert River

Formation and Dalrymple Sandstone aquifers, particularly to the south of the region. In the Bathurst Range however, the

presence of the Normanton Formation sandstone means that useful supplies of reasonable quality water are available.

Groundwater of the Normanton Formation also discharges to springs throughout the year, thus maintaining various

wetland habitats (Horn et al., 1995). Outcrop of the Rolling Downs Group is limited, occurring only as remnant hills,

exposures in the Bathurst Range and in the sides of the Fairview Plateau. Formation thickness varies from 40 to 200 m

in the centre of the basin. Hydraulic parameters have only been documented for two bores screened in the Rolling

Downs Group, with transmissivities up to 500 m2/day. The unconfined water levels range from zero to 75 mBGL and the

confined (artesian) water levels range of zero to 5 mAGL.

Cainozoic aquifers

Across much of the Northern Coral region, the surface geology comprises a veneer of Quaternary and Tertiary

sediments. These deposits are relatively thin and often consist of clayey and or silty materials that make poor aquifers. In

general, there is little known about the water table behaviour of these deposits, however large seasonal variations are

thought to occur, with aquifers emptying during some dry seasons (Horn et al., 1995).

The Quaternary deposits mainly comprise alluvium and coastal marine deposits including beach sands and dunes. The

Tertiary sediments generally consist of quartz sand and ferricrete and are characterised by a deep weathering profile.

Previously, the Laura Township sourced a small supply (less than 2 L/second) from the Tertiary sediments; however, this

is no longer the case and hence there are no other known occurrences of groundwater extraction from these sediments.

Although the Tertiary sediments are restricted laterally, they can reach thicknesses of 70 m (Horn et al., 1995).

For the river basins in the north of the region (i.e. the Jacky Jacky, Olive-Pascoe, Lockhart, Stewart, Normanby and

Jeannie) there are no data available for unconsolidated sediments, apart from broad scale geological maps. From these,

it appears that sediments are of colluvial or alluvial origin. McEniery (1980) recognised the potential for supplies in some

of the more extensive flood plains such as the Stewart River.

For the river basins further south (i.e. the Endeavour, Daintree and Mossman) McEniery (1980) estimated the thickness

of the alluvial deposits to range from 2 to 30 m and have a maximum saturated thickness of up to 20 m.

Transmissivities of the unconsolidated sediments in the Mossman River Basin range from 15 to 400 m2/day. A storage

coefficient of 10-4 and a specific yield of 10 to 12 percent has been recorded (McEniery, 1980).

NC-2.3.2 Inter-aquifer connection and leakage

There is a potential for inter-connection between the underlying GAB aquifers and the overlying Cainozoic sediments.

Upward vertical leakage is likely to occur from the Gilbert River Formation and Dalrymple Sandstone aquifers to the

overlying alluvial sediments where the confining beds are thin and hydraulic gradients high. These conditions

predominate near the basin margins.


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NC-2.3.3 Recharge, discharge and groundwater storage


Fractured rock aquifers are recharged via the vertical infiltration of rainfall where the basement outcrops. Recharge to

fractured zones will be rapid in areas where fractures persist to great depths. The dominant form of recharge to the

fractured rock aquifers, however, will occur where fractures are exposed in ephemeral streams that flow during the wet

season (AGE, 2007).


Recharge to the GAB aquifers is by infiltration of rainfall and leakage from streams into outcropping sandstone. In the

Northern Coral region, this primarily occurs at the ring of Mesozoic outcrop areas in the Laura Basin and across the

entire portion of the Carpentaria Basin that resides to the north of this region. These areas are commonly referred to as

‘recharge beds’ or ‘intake beds’ (Figure NC-3).

Kellett et al. (2003) investigated recharge processes within the Queensland GAB intake beds from Goondiwindi in the

south to approximately 150 km north of Torrens Creek, which is south of the Northern Coral region. This investigation

identified three primary recharge mechanisms: diffuse rainfall, preferred pathway flow and localised recharge beneath

rivers, creeks and alluvial groundwater systems overlying the intake beds.

Preferred pathway flow involves the movement of water through conduits such as: fissures, joints, remnant tree roots or

highly permeable sediments and is considered the dominant recharge process for the intake beds. The rate of recharge

via preferred pathway flow is dependent upon the frequency of high magnitude rainfall events, and will be high in the

Northern Coral region due to the very high annual rainfall in far north Queensland.

Discharge from the GAB occurs in a number of ways, including:

natural discharge from springs

fault controlled and diffuse upward vertical leakage from aquifers towards the regional watertable

baseflow to rivers in outcrop areas

subsurface outflow to the Coral Sea

artificial discharge, via artesian flow and pumped extraction from wells drilled into aquifers.

Springs are quite common in the recharge areas to the north of the Northern Coral region and are mainly associated with

‘overflow’ or the ‘rejection’ of recharge into aquifers, or from the interaction between the local topography and the

watertable. The locations of the groundwater springs in the Northern Coral region are shown in Figure NC-3. Flowing

springs are also typically associated with faults along which the groundwater flows upwards, with the abutment of

aquifers against low hydraulic conductivity bedrock and with pressure water breaking through thin confining beds near

the discharge margin of the basin. Minor freshwater beach springs also occur along the eastern coastline.

Submarine groundwater discharge occurs from the GAB via depressions in the seabed along the inner shelf of the Great

Barrier Reef. Springs commonly known as ‘wonky holes’ occur off the Queensland coast between Townsville and Cape

York. A study conducted by Stieglitz and Ridd (2000) identified over 100 wonky holes within 7 to 10 km of the coast with

depressions 10 to 30 m in diameter and up to 4 m in depth.

Cainozoic Aquifers

Recharge to the alluvial aquifers is predominantly via the direct infiltration of rainfall. River valley alluvium receives

recharge via lateral flow through the sandy river beds during the wet season high river flows. Vertical infiltration occurs

on the extensive floodplain when the river floods, and upward vertical leakage from the GAB aquifers occurs where

confining layers are thin and hydraulic gradients are high.

Alluvial deposits also receive recharge through the beach ridges and conversely, leakage of the beach ridge aquifers is

likely to occur through the alluvial sediments (Horn et al., 1995).

Discharge from the alluvium predominantly occurs in the form of evapotranspiration; however, during the dry season

discharge to the rivers also occurs in the form of baseflow.


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NC-2.3.4 Groundwater quality


Fractured rock aquifers of the Hodgkinson Formation provide good quality groundwater, but in some coastal areas the

aquifers in the metamorphic rocks have been influenced by seawater (Horn et al., 1995).

The Department of Environment and Resource Management (DERM) recorded groundwater quality for 75 bores

constructed in the Hodgkinson Formation (depths from 4 to 260 m) between 1974 and 1992. Groundwater salinity ranged

from 30 to 48,700 µS/cm and the median reading was 150 µS/cm electrical conductivity (EC).


Groundwater quality in the Gilbert River Formation and the Dalrymple Sandstone is generally acceptable for most

purposes. Figure NC-15 shows groundwater salinity for approximately 300 bores in the region, which have salinity

reading dates ranging from 1974 to 2000. Approximately 40 percent of the bores have a recorded depth and these range

between 4 and 294 m; hence the salinity distribution map represents several aquifers. The majority of the bores indicate

that the groundwater is fresh and less than 750 µS/cm EC. This is because much of the region comprises part of the

primary recharge area for the GAB (i.e. the intake beds). Department records for 21 bores constructed in the Gilbert

River Formation and Dalrymple sandstone aquifers (depths from 4 to 55 m) reveal a salinity (as electrical conductivity)

range from 39 to 820 µS/cm between 1977 and 1999.

Groundwater from the Rolling Downs Group is generally of poorer quality and only suitable for stock watering.

Conversely, groundwater quality of spring flows from the Normanton Sandstone Formation (of the Rolling Downs Group)

is of excellent quality. Department records for one bore from the Normanton Formation show an average EC of 72 µS/cm.

There are five other bores from the Rolling Downs Group (depths from 22 to 68 m) with salinity measurements between

1987 and 1997. Groundwater salinity ranged from 230 to 2620 µS/cm.

Cainozoic aquifers

In the absence of any quantitative groundwater quality information, McEniery (1980) assumed that groundwater quality in

the Daintree River Basin would be less than 1000 mg/L Total Dissolved Solids (TDS) (~ 1600 S/cm EC) and less than

500 mg/L TDS (~ 800 S/cm) in the Mossman River Basin. Shallow aquifers are also at high risk from point source

contamination, particularly in the Laura Basin (Horn et al., 1995).

DERM provided groundwater quality information for 32 bores constructed in the Cainozoic aquifers in the region. This

included salinity measurements from Cainozoic aquifers described as alluvium, Cainozoic sediments, coastal alluvium,

Mossman River alluvium and the Mowbray River alluvium. The depths of these bores ranged from 19 to 61 m and

reading dates ranged from 1976 to 2000. Groundwater salinity measurements ranged from

52 to 6800 µS/cm EC, with a median of 230 µS/cm EC.


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Figure NC-15. Groundwater salinity distribution for all bores drilled in the Northern Coral region


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NC-2.4 Legislation, water plans and other arrangements

NC-2.4.1 Legislated water use, entitlements and purpose

The Water Act (2000) provides a regulatory framework for water resource planning, management and supply. The

Queensland Department of Environment and Resource Management (DERM) administers the Act through the regulation

of water and sewerage services and the establishment and operation of water authorities. The Water Act establishes a

system for the planning, allocation and use of water through the development and implementation of Water Resource

Plans and Resource Operation Plans.

Water Resource Plans establish the overall water allocation framework for a catchment, and may include overland flow

and sub-artesian as well as riverine waters. They set water allocations for current and future users, as well as an

environmental allocation to sustain the ecological health of aquatic ecosystems. A Resource Operation Plan provides the

detailed rules to implement the water resource plan. These rules include the operation and management of water

services, allocation of tradable water allocations and monitoring of use and environmental outcomes.

The development of water resource plans incorporates technical advice on the flow requirements to sustain ecosystems

and their dependent flora and fauna. Community consultation involves a community reference panel as well as wider

community engagement and review.

The Water Resource (Great Artesian Basin) Plan 2006 (listed under the Water Act 2000) (DERM, 2006) defines the

management areas of the GAB and has the following key strategies:

protection of the GAB-dependent springs and base flows

volumetric licensing of non-stock and domestic entitlements (other than mine dewatering)

stock and domestic licenses remain non-volumetric but stock and domestic use should become more efficient

over time as bores are capped and piped under the GAB Sustainability Initiative program

target-pressure levels from water saved through bore capping

release of unallocated water in response to demand, and the state holds a reserve for major projects.

The region includes part of the Cape and Laura management areas of the Water Resource (Great Artesian Basin) Plan

2006 (DERM, 2006) (Figure NC-16) and part of the Gulf management area. These areas have relatively small allocations

for future development, and the intent is to conservatively manage these resources because of the significant cultural

and environmental assets. The key features of the Water Resource (Great Artesian Basin) Plan 2006 for the Northern

Coral region are:

significant protection of springs (no drilling within 5 km of a spring)

capacity of existing users to pay for water allocations e.g. small enterprises, Indigenous communities and Cook

Shire.

The DERM does not intend in the foreseeable future to undertake additional water resource planning activities within the

Northern Coral region due to the low development pressures on the water resources in this region.

Groundwater in the Laura Basin provides reliable supplies of water to most of the region. Approximately 95 percent of the

population depends on groundwater for drinking and domestic purposes, primarily in the dry season, when surface water

resources diminish (Horn et al., 1995).

Groundwater entitlement volumes and estimated stock and domestic use volumes were reported as part of the Water

Resource (Great Artesian Basin) Plan 2006 (DERM, 2006). This information was collated in terms of the Management

Areas defined for the GAB in Queensland and has been reconfigured by the DERM to estimate volumes for the project

regions. For the Northern Coral region the estimated volume of stock and domestic use is approximately 1 GL/year and

the estimated volume of licensed entitlements is about 13 GL/year (). The main non-stock and domestic entitlement is a

single volume associated with the Laura Town Water Supply (160 ML/year). The table shows that most of the stock and

domestic use is sourced from the Palaeozoic rocks (i.e. 40 percent) and the GAB aquifers (i.e. 35 percent). Licenced

entitlements are predominantly assigned to the Cainozoic aquifers (i.e. approximately 70 percent).


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Table NC-3. Estimated stock and domestic groundwater use and groundwater entitlements for the Northern Coral region

Formation Stock and domestic use Entitlement

GL/y

Quaternary alluvium 0.06 1.243

Quaternary alluvium 0.06 1.243

Cenozoic sediments/basalt 0.17 8.561

Jurassic – early cretaceous Great Artesian Basin aquifers

0.35 0.172

Paleozoic rocks 0.40 2.581

Proterozoic rocks 0.01 0.000

Total volume 1.00 12.557

Five river basins in the Northern Coral region are either declared or potential wild river areas. The Wild Rivers Act 2005

includes a process for the Minister for Natural Resources to declare wild river areas. The intent of the legislation it

preserve the natural values of rivers that have all or almost all of their natural values intact - wild rivers. It does this by

regulating most future development activities and resource allocations within a declared wild river and its catchment - the

wild river area. A wild river declaration will include water allocation limits by including unallocated water held in reserves

for specific purposes. New development activities will be regulated through existing development assessment process

with wild river requirements applied through a wild river declaration or the wild rivers code. Development and

authorisations in place at the time a declaration is made are not affected and continue.


Although groundwater yields from the fractured rock aquifers are generally low, a number of stock and domestic water

requirements are met from this aquifer, particularly where it is found at shallow depths.


The GAB aquifers in the Northern Coral region are managed through the Water Resource (Great Artesian Basin) Plan

2006 and are predominantly represented by the Laura Management Area, which covers the confined and unconfined

Gilbert River Formation aquifers (and equivalents). The northern part of the region is represented by a small portion of

the Cape Management Area. This incorporates the Rolling Downs Group and the Gilbert River Formation (and

equivalents). The locations of the Queensland management areas are shown in Figure NC-16.

Groundwater is extracted from the Gilbert River Formation for limited stock and domestic and conservation use and the

same aquifer supplies the township of Laura. Stock and domestic use is limited however, given the depth of drilling -

most bores are located in the vicinity of the intake beds, where the aquifers are closer to the surface.

The Dalrymple Sandstone aquifers have not been widely developed, as most bores are constructed in the overlying

Gilbert River Formation.

Cainozoic aquifers

The beach ridge and coastal dune deposits found along the coastline, as well as the floodplain and stream bed deposits

associated with rivers, are all characterised by groundwater of variable quality. Little research has been carried out on

these deposits, as they provide only a limited amount of groundwater for stock watering and domestic use. Although the

Laura town water supply was previously obtained from a shallow Tertiary aquifer (Horn et al., 1995) this is no longer the

case.


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Figure NC-16. Groundwater management areas in the Northern Coral region

NC-2.4.2 Rivers and storages

There are no major storages on any rivers in the region.

NC-2.4.3 Unallocated water

The Lockhart basin and Stewart basin wild river declaration include reserve of unallocated water. Under the Cape York

Peninsula Heritage Act 2007 a wild river declaration must provide a reserve of water in the area to which the declaration

relates for the purpose of helping Indigenous communities in the area achieve their social and economic aspirations. This

is known as the Indigenous reserve. The Lockhart basin wild river declaration provides for 5 GL/year as the Indigenous

reserve, 2 GL/year for the Strategic reserve and 0.5 ML/year for the General reserve. The Stewart basin wild river

declaration provides for 4000 ML/year for the Indigenous reserve, 800 ML/year for the Strategic reserve and 200 ML/year

for the General reserve.


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NC-2.4.4 Social and cultural considerations

For Aboriginal peoples the Cape York Peninsula and its surrounding waters represent clan estates. The land and

surrounding waters formed the basis of the local Aboriginal economy and culture, with a history going back over tens of

thousands of years. The Torres Strait Islanders also have had a significant relationship with the area for over a thousand

years. Non-Indigenous settlement has been associated with mining and pastoralism, which began with an initial wave of

settlement in the 1870s.

The cattle industry, which occupies over a million hectares across the region is only marginally productive. This is due

largely to the low soil fertility, poor nutrient value of pasture species, isolation and limited infrastructure.

A report by Balkanu Cape York Development Corporation notes that the cultural significance of areas in this region has

not been comprehensively documented (Standley and Roberts, 2007). The Balkanu Corporation has developed a

framework for Cultural Water Quality Indicators with case studies undertaken for Lakefield National Park, Buru and

Mossman Gorge, Injinoo and Aurukun. The report describes the cultural significance, environmental condition, pressure,

management aspirations, and indicators for numerous key places within the Lakefield area: Ngo Coom (Big Water)

Saxby Lagoon, Ngoldin – Pelican Lake, Argnuwal – 18 Mile Lagoon, Rocky Crossing – Hahn River crossing, Spring at

Mary Valley.

The report notes:

“Kuku Thaypan country contains wetlands and lakes that are listed as nationally important in the

Directory of Important Wetlands and form the majority of the Lakefield aggregation…. Lagoons along

the Morehead River drainage and specifically two places in the area of Ngo Coom/Ngokumina (Saxby

Lagoon) in Kuku Thyapan country are home to Alpa payrrape (Mermaid) a traditional story about

young girls that extends all the way to the border with Lama Lama country at Hahn River crossing

and begins at Argnuwal (18 Mile). Girls are not allowed to eat mussels from these two places located

near Ngo Coom and the Morehead River specifically, as to do so may harm the health of their babies.

Barramundi may be caught and eaten there. The water at these two places is clean and never dries

up as the spirits of the mermaid there maintains it...”

The lagoons in Morehead River drainage are incredibly important places of cultural, spiritual and environmental diversity,

they are refugia areas during the dry and seed to the surrounding landscape during the wet.

In Kuku Yalandji country around Mossman Gorge, key sites are described – Mossman Gorge itself, and the Roaring Meg

Falls – Kidja.

The area is sparsely populated. The largest urban populations (excluding Thursday Island) are Port Douglas (population:

948) and Cooktown (1411). The region includes the Aboriginal and Torres Strait Islander settlements of Lockhart River,

Aurukun, Mapoon, Pormpuraaw, Hopevale and Bamaga.

NC-2.4.5 Changed diversion and extraction regimes

There are no major diversions or extraction schemes in the region.

NC-2.4.6 Changed land use

The region is not extensively cleared, as agricultural production does not occur in most of the area. The potential for

future economic-based developments such as those associated with improved pasture and cropping, could pose a threat

to land systems (Sattler & Williams, 1999). Invasive exotic weed species and cane toads also pose a threat. Feral pigs,

horses, cane toads and feral cats are found throughout the region. The region has fewer pest species than other tropical

savannah regions, however, and pigs have the most widespread impact on the natural environment and pastoral

properties, with the most significant damage occurring along the coast. Feral horses impact on pastoral activities and

feral cats are thought to affect native wildlife populations. The cane toad had spread to the tip of Cape York by about

1994. Fallow deer are also present in isolated pockets.


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NC-2.4.7 Environmental and legislative constraints and implications of future development

The Environmental Protection Act (1994) is administered by the DERM. The object of the Act is to protect the

environment while allowing for ecologically sustainable development. Generally, in the context of water quality and river

health, the Act is administered to regulate point-source discharges, but could apply to diffuse discharges (Kroon et al.,

2004).

The associated Environmental Protection (Water) Policy (1997) sets out the process to establish environmental values

and water quality objectives consistent with the National Water Quality Management Strategy. Environmental values are

the qualities of waterways that need to be protected such as water suitability for agriculture, recreation, drinking water

and also for the protection of aquatic ecosystems. Values set for the protection of aquatic ecosystems reflect the

condition of those rivers – from high ecological values to moderately or highly disturbed systems. Water quality

objectives, such as a particular level of nutrients for example, can then be set to maintain those values. The objectives

are defined using the Queensland Water Quality Guidelines (EPA, 2006) developed from regional reference sites. EPA

has prepared a guideline for establishing environmental values and water quality objectives. Environmental values and

water quality objectives can be scheduled under the Act, which requires State and Local Governments to consider them

in relation to development approvals and licenses.

The Wild Rivers Act (2005) is administered by the DERM. The objective of the Act is to preserve the natural values of

wild rivers by regulating most future development activities within the declared wild river and its catchment area. The

intent is to protect rivers that have intact natural values against any further loss of those values. Under the Act, the

Minister can propose a river for declaration. The declaration proposal is released for public comment (a minimum period

of 20 working days is allowed for comment). A moratorium on water allocation, vegetation clearing and mining approvals

is imposed while the declaration proposal is being prepared and resolved.

If the Minister chooses to proceed with the declaration following the consultation process, new development activities will

be regulated through the development assessment codes, water caps and release strategies associated with the final

declaration. The codes then trigger the amendment of other acts to recognise the declaration and:

prohibit new development in sensitive areas

recognise the codes in assessments, for example, under the Integrated Planning Act

make general agricultural activities assessable.

The assessment and compliance responsibilities remain with the other acts. The declaration specifies the extent of the

wild river and its management areas, and any rules or limits that must be observed in the declared area for assessment

of activities (such as building, agriculture or mining). Maps will specify the wild river, its catchment and special features

such as wetlands and floodplains. The wild river and its special features (with up to a 1 km buffer zone) are classified as

a high preservation area. The rest of the catchment is considered a preservation area. The declaration may set water

allocation limits for various uses, and sets development limits and codes for various activities. Future development

applications will then be assessed in terms of potential impacts on flows, river geomorphology, water quality, riparian

function and wildlife.

The high preservation area (the wild river, special features and buffer zone) will prohibit new dams and weirs, mining and

exploration, agriculture other than grazing, animal husbandry and aquaculture, environmentally relevant activities

(defined under the Integrated Planning Act), or clearing of native vegetation. The preservation area (the wild river

catchment) will prohibit new instream mining, stream alignments, dams (unless for stock or domestic), ponded pasture

structures, levees etc. In addition water allocation limits and stringent assessment of all other new developments will be

applied. Activities that do not presently require resource allocation or development approval such as recreational fishing,

traditional Indigenous activities or rangeland grazing will not be affected.


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NC-2.5 References

Abrahams H, Mulvaney M, Glasco D and Bugg A (1995) Areas of Conservation Significance on Cape York Peninsula. Australian Heritage Commission.

ACRES (2000) ACRES Landsat 7 Mosaic of Australia, 1999–2000. Australian Centre for Remote Sensing. Australian Government - Geoscience Australia, Canberra.

AGE (2007) Far North Queensland Water Strategy Groundwater Aspects. Prepared for the Department of Natural Resources and Mines, March 2007. Australasian Groundwater & Environmental Consultants.

Bain JH and Draper JJ (1997) North Queensland Geological Survey Organisation Bulletin 240 and Queensland Department of Minerals and Energy Queensland Geology 9.

BRS (2002) Land use of Australia, Version 3, 2001/2002. Australian Government Bureau of Rural Sciences. Metadata at <http://adl.brs.gov.au/anrdl/php/full.php?fileidentifier=http://adl.brs.gov.au/findit/metadata_files/pa_luav3r9eg__00112a06.xml>

Bucher D and Saenger P (1989) An Inventory of Australian Estuaries and Enclosed Marine Waters. Unpublished report to Australian Recreational and Sport Fishing Confederation.

DEWR (2005) Australia - Present Major Vegetation Groups - NVIS Stage 1, version 3. Australian Government Department of the Environment and Water Resources. http://www.environment.gov.au/erin/nvis/mvg/index.html.

DNRM (2005) Hydrogeological framework report for the Great Artesian Basin resource plan area. Queensland Department of Natural Resources and Mines.

Environment Australia (2001) A directory of important wetlands in Australia. Environment Australia, Canberra, Third Edition. Available at < http://www.environment.gov.au/water/publications/environmental/wetlands/pubs/directory.pdf >.

Herbert B, Peeters J, Graham P and Hogan A (1994) Fish Fauna Survey Project: Final Report. Department of Primary Industries.

Horn AM, Derrington EA, Herbert GC, Lait RW and Hillier JR (1995) Groundwater Resources of Cape York Peninsula. Strategy office of the co-ordinator general of Queensland, Brisbane, Department of the Environment, Sport and Territories, Canberra, Queensland Department of Primary Industries, Brisbane and Mareeba, and Australian Geological Survey Organisation, Mareeba.

Kellett JR, Ransley TR, Coram J, Jaycock J, Barclay DF, Mcmahon GA, Foster LM and Hillier JR (2003) Groundwater Recharge in the Great Artesian Basin Intake Beds, Queensland, Final Report for NHT Project #982713 Sustainable Groundwater Use in the GAB Intake Beds, Queensland, BRS, Natural Resources and Mines, Queensland Government.

Kroon F, Bormans M, Ford P, Gehrke P and Molloy R (2004) Review of Queensland Government water quality and aquatic health monitoring and information requirements. CSIRO Land and Water Client Report to the Environmental Protection Agency.

Le Cussan J (1993) Key Conservation Areas: Far Northern Region. Department of Environment and Heritage, Cairns.

McEniery MB (1980) Groundwater resources - north Queensland. IN Henderson R.A. & Stephenson P.J.(Eds) - The geology and geophysics of northeastern Australia. Geological Society of Australia. Queensland Division 1v p435-445

Neldner VJ and Clarkson JR (1995) Vegetation Survey Mapping of Cape York Peninsula. In: Cape York Peninsula Land Use Strategy. Office of the Co-ordinator General and Department of Environment and Heritage, Government of Queensland, Department of Environment, Sport and Territories and Australian Geological Survey Organisation, Canberra.

Sattler P and Williams R (eds) (1999) The Conservation Status of Queensland’s Bioregional Ecosystems, Environmental Protection Agency, Brisbane, Queensland.

Stieglitz T and Ridd P (2000) Submarine Groundwater Discharge from Paleochannels? Wonky Holes on the Inner Shelf of the Great Barrier Reef, Australia. Conference Proceedings HYDRO 2000, Perth, 20 – 23 November 2000.

Taplin LE (1987) The Management of Crocodiles in Queensland, Australia. In: Wildlife Management: Crocodiles and Alligators (eds Webb GJW, Manolis SC and Whitehead PJ). Surrey Beatty and Sons/Conservation Commission of the Northern Territory.

Willmott WF, Powell S, Mifsud JM (1976) Orford Bay, Queensland, 1:250 000 geological series map. Sheet SC/54-16, 1st edition. Bureau of Mineral Resources, Australia & Geological Survey of Qld 1v.

Willmott WF and Powell BS (1977) Cape Weymouth, Queensland, 1:250 000 geological series map. Sheet SD/54-04. Bureau of Mineral Resources, Australia & Geological Survey.


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NC-3 Water balance results for the Northern Coral

region

This chapter describes modelling results and the assessment of the water resources undertaken by this project for the

Northern Coral region. Detailed, quantified assessments are made where possible, and relevant, and confidence is

estimated. Modelling results are reported under climate and development scenarios as defined at the division level in

Section 2.1 of Chapter 2. This chapter is sub-divided into:

climate

recharge estimation

conceptual groundwater models

groundwater modelling results

rainfall-runoff modelling results

river system water balance

changes to flow regimes at environmental assets.

NC-3.1 Climate

NC-3.1.1 Historical climate

The Northern Coral region receives an average of 1338 mm of rainfall over the September to August water year (Figure

NC-17), most of which (1233 mm) falls in the November to April wet season (Figure NC-18). Annual rainfall is highest

along the coast (Figure NC-17), ranging between 3640 mm in the south-east and 917 mm further inland. Over the

historical (1930 to 2007) period, annual rainfall has been gradually increasing from an initial average of around 1250 mm

to approximately 1400 mm later in the period. The highest regional average yearly rainfall received was 2143 mm which

fell in 1974, and the lowest was 769 mm in 1961.

Areal potential evapotranspiration (APET) is very high across the region, averaging 1853 mm over a water year (Figure

NC-17), and varies little across the seasons (Figure NC-18). APET generally remains higher than rainfall for most of the

year resulting in near-year-round water-limited conditions. The exceptions to this are the months of January to March,

when more rain falls than can potentially be evaporated.


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Figure NC-17. (a) Historical annual rainfall and (b) its divergence from the long-term mean; and (c) historical annual areal potential

evapotranspiration and (d) its divergence from the long-term mean averaged over the Northern Coral region

(a) (b)

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Figure NC-18. Historical mean monthly (a) rainfall and (b) areal potential evapotranspiration and their temporal variation (range and ±

one standard deviation) averaged over the Northern Coral region


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Figure NC-19. Spatial distribution of historical mean annual (water year), wet season and dry season rainfall and areal potential

evapotranspiration (potential evaporation) and their difference (rainfall less areal potential evapotranspiration ancross the Northern

Coral region

NC-3.1.2 Recent climate

Figure NC-20 compares recent (1996 to 2007) to historical (66-year period 1930 to 1996) mean annual rainfall for the

Northern Coral region. Across the whole region, recent rainfall is between zero and 20 percent higher than historical

rainfall – with very few areas having experienced a statistically significant change in rainfall.


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(a) (b)

(c) (d)

Figure NC-20. Spatial distribution of (a) historical and (b) recent mean annual rainfall; and (c) their relative percent difference and (d) the

statistical significance of these differences across the Northern Coral region

NC-3.1.3 Future climate

Under Scenario C annual rainfall varies between 1218 and 1508 mm (Table NC-4) compared to the historical mean of

1338 mm. Similarly, APET ranges between 1880 and 1921 mm compared to the historical mean of 1853 mm.

A total of 45 variants of Scenario C were modelled (15 GCMs for each of the high, medium and low global warming

scenarios). Subsequently, results from an extreme ‘wet’, median and extreme ‘dry’ variant are shown (referred to as

scenarios Cwet, Cmid and Cdry). Under Scenario Cwet annual rainfall and APET increase by 13 percent and 1 percent,


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respectively. Under Scenario Cmid annual rainfall increases by 1 percent and APET increases by 2 percent. Under

Scenario Cdry annual rainfall decreases by 9 percent and APET increases by 4 percent.

Under Scenario Cmid long-term monthly averages of rainfall and APET do not differ much from historical values (Figure

NC-21). Under Scenario Cmid rainfall lies well within the range in values from all 45 future climate variants. The

seasonality of both rainfall and APET changes little. Under Scenario Cmid APET is consistently higher than historical

values and lies within the range in values derived from all 45 future climate variants.

The spatial distributions of rainfall and APET under Scenario C are compared to the historical distribution in Figure NC-

22 and Figure NC-23. Under Scenario C the coast-to-interior gradient in rainfall is retained, but with the greatest changes

in rainfall occurring along the coast. The spatial distribution of APET under Scenario C is similar to the highly

regionalised historical distribution. The greatest changes to APET occur in the inland portions of the Kimberley region.

Table NC-4. Mean annual (water year), wet season and dry season rainfall and areal potential evapotranspiration averaged over the

Northern Coral region under historical climate and Scenario C

Water year* Wet season Dry season

mm/y mm/season

Rainfall

Historical 1338 1233 105

Cwet 1508 1383 108

Cmid 1350 1226 108

Cdry 1218 1118 87

Areal potential evapotranspiration

Historical 1853 989 864

Cwet 1880 994 884

Cmid 1893 1009 881

Cdry 1921 1028 890

* Note that the sum of the wet season and dry season values does not always equal the water year values because the combined wet season and dry season period (November to October) is different to the water year period (September to August).

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Figure NC-21. Mean monthly (a) rainfall and (b) areal potential evapotranspiration averaged over the Northern Coral region under

historical climate and Scenario C (C range is pooled from the 45 Scenario C simulations (15 global climate models and 3 global

warming scenarios) – the lower and upper limits in C range are therefore not the same as scenarios Cdry and Cwet)

NC-3.1.4 Confidence levels

Analysis of confidence of the climate data is presented at the division level and is reported in Section 2.1.4.


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Figure NC-22. Spatial distribution of mean annual (water year), wet season and dry season rainfall across the Northern Coral region

under historical climate and Scenario C


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Figure NC-23. Spatial distribution of mean annual (water year), wet season and dry season areal potential evapotranspiration averaged

over the Northern Coral region under historical climate and Scenario C


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NC-3.2 WAVES potential diffuse recharge estimations

The WAVES model (Zhang and Dawes, 1998) was used to estimate the change in groundwater recharge across the

Northern Coral region under a range of different climate scenarios. WAVES is a vertical recharge flux model that can

model plant physiological feedbacks in response to increased CO2, as well as modelling the water balance of different

soil, vegetation and climate regimes. It was chosen for its balance in complexity between plant physiology and soil

physics. It was also used to assess recharge for the Murray-Darling Basin Sustainable Yields Project (Crosbie et al.,

2008).

NC-3.2.1 Under historical climate

The calculated historical recharge for the Northern Coral region is greatest in the north and east of the region. The

historical record was assessed to establish any difference between wet and dry periods of recharge. A 23-year period

was used, which allows projections of recharge estimates to 2030 – in other words, to estimate recharge in 2030

assuming future climate is similar to historical climate (Scenario A). Under a wet historical climate (Awet) recharge

increases 13 percent. Under the median estimate of historical climate (Amid) recharge decreases 3 percent. Under a dry

historical climate (Adry) recharge decreases 14 percent.

Table NC-5. Recharge scaling factors in the Northern Coral region for scenarios A, B and C

Region Awet Amid Adry B Cwet Cmid Cdry

Northern Coral 1.13 0.97 0.86 0.98 1.37 1.11 1.02


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Figure NC-24. Spatial distribution of historical mean recharge rate; and recharge scaling factors across the Northern Coral region for

scenarios A, B and C


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NC-3.2.2 Under recent climate

The recent (1996 to 2007) climate in the Northern Coral region has been wetter than the historical (1930 to 2007)

average but the calculated recharge decreases 2 percent under Scenario B relative to Scenario A (Table NC-5). This

decrease has not been spatially uniform with some areas of the north and south of the region showing an increase in

recharge (Figure NC-24).

NC-3.2.3 Under future climate

Figure NC-25 shows the percentage change in modelled mean annual recharge averaged over the Northern Coral region

under Scenario C relative to Scenario A for the 45 scenarios (15 GCMs for each of the high, medium and low global

warming scenarios). The percentage change in the mean annual rainfall and recharge from the corresponding GCMs are

also tabulated in Table NC-6. In some scenarios the recharge is projected to increase despite a decrease in rainfall. This

is because total rainfall is not the only climate variable that influences recharge. Daily rainfall intensity, temperature and

CO2 concentration are also important drivers (see Section 2.3.3 in the division-level Chapter 2), and specific situations

can result in this counter-intuitive result. In particular, rainfall intensity is seen as a significant factor in this relationship.

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Figure NC-25. Percentage change in mean annual recharge under the 45 Scenario C simulations (15 global climate models and three

global warming scenarios) relative to Scenario A recharge

Table NC-6. Summary results under the 45 Scenario C simulations (numbers show percentage change in mean annual rainfall and

recharge under Scenario C relative to Scenario A)

High global warming Medium global warming Low global warming

GCM Rainfall Recharge GCM Rainfall Recharge GCM Rainfall Recharge

mri -7% -7% mri -5% -6% mri -3% -4%

csiro -8% 2% csiro -6% 1% csiro -4% 1%

ncar_pcm 4% 8% ncar_pcm 4% 7% ncar_pcm 3% 5%

giss_aom 0% 10% giss_aom 1% 7% giss_aom 1% 5%

miroc 1% 10% miroc 2% 8% miroc 2% 5%

ncar_ccsm 5% 11% ncar_ccsm 4% 7% ncar_ccsm 4% 5%

inmcm 3% 13% inmcm 3% 10% inmcm 2% 6%

ipsl 4% 16% ipsl 3% 11% ipsl 3% 8%

iap 3% 16% iap 3% 13% iap 2% 8%

cnrm 4% 17% cnrm 3% 12% cnrm 3% 9%

mpi 0% 23% mpi 0% 18% mpi 1% 11%

miub 4% 26% miub 4% 20% miub 3% 12%

cccma_t63 15% 28% cccma_t63 12% 22% cccma_t63 9% 16%


gfdl 1% 59% gfdl 1% 41% gfdl 2% 26%


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Under Scenario Cwet recharge increases 37 percent. Under Scenario Cmid recharge increases 11 percent. Under

Scenario Cdry recharge increases 2 percent. The fact that recharge rates are higher when rainfall is similar to the

historical value reflects the importance of climate variables other than total rainfall in determining recharge (e.g. rainfall

intensity and temperature). Due to the way the GCMs were selected for scenarios Cwet and Cdry, an area near the tip of

Cape York is calculated to have a decrease in recharge under Scenario Cwet and an increase in recharge under

Scenario Cdry.


The estimation of recharge from WAVES is only indicative of the actual recharge and has not been validated with field

measurements. A steady state groundwater chloride mass balance (CMB) has been conducted as an independent

measure of recharge (Crosbie et al., 2009). The results in the Northern Coral region show that the historical estimate of

recharge using WAVES (271 mm/year) is more than the best estimate using the CMB (125 mm/year) and is outside the

confidence limits of the CMB (48 to 221 mm/year). Detailed field investigations will be the only way to resolve this

uncertainty.

NC-3.3 Conceptual groundwater models

The Northern Coral region encompasses the fractured rock aquifers of the Coen Inlier and Hodgkinson Province, and the

Great Artesian Basin (GAB) aquifers including a small portion of the Carpentaria Basin in the north and the entire Laura

Basin in the south. Cainozoic deposits form a veneer over much of the region; however, these are not considered a

significant groundwater resource due to the variability in thickness, saturation and quality.

The GAB Gilbert River Formation aquifers are the dominant groundwater resources in this area. Gilbert River Formation

aquifers are confined by the Rolling Downs Group in the Laura Basin and are unconfined in the Carpentaria Basin. The

portion of the Carpentaria Basin that exists within the Northern Coral region comprises GAB intake beds, which are

considered a primary area of recharge for the GAB. In the Laura Basin, intake beds outcrop in a ring around its eastern

margin. Recharge to the intake beds predominantly occurs by means of rainfall infiltration via preferred pathway flow.

Groundwater discharge primarily occurs as lateral outflow into the Coral Sea. It will also occur via upward vertical

leakage to overlying units, as discharges to springs in the north of the region and as offshore discharge e.g. via wonky

holes. A relatively negligible volume of groundwater discharge occurs in the form of groundwater extraction.

Groundwater discharge also occurs as baseflow to rivers, where rivers are incised into the outcropping GAB aquifers in

the area of the intake beds. Streamflows in a number of rivers in the Northern Coral region persist into the dry season

due to groundwater discharge, including the Normanby, Laura, Little Laura, Hann, Olive, Pascoe, Kennedy and Marrett.

Flow continues throughout the entire year in the Hann River only (Horn et al., 1995).

The GAB aquifers interact with both the underlying fractured rock aquifers and the overlying alluvial aquifers. The Gilbert

River Formation (and equivalents) directly overlies the basement rocks, allowing a limited volume of recharge to the GAB

aquifers via upward vertical leakage from the fractured rock aquifers. Discharge from the GAB to the overlying alluvial

aquifers primarily occurs near the basin margins, where the overlying confining layers are thin and the hydraulic

gradients from the GAB aquifers are high.

NC-3.3.1 Baseflow index analysis

The results of the baseflow analysis for suitable gauges in the Northern Coral region are provided in Table NC-1. The

annual baseflow index (BFI) values range from 0.09 to 0.39 (n=11). Figure NC-2 shows the surface geology of the

Northern Coral region and the average volume of dry season baseflow in rivers. The volume of dry season baseflow is

highly variable in this region, ranging from less than 1 to 200 GL/year. Figure NC-2 also highlights the significance of

groundwater discharge to streams occurring from the older fractured rock aquifers. It shows large baseflow volumes

determined for stream gauges 108002A and 107002A, which are located on streams that incise the Hodgkinson

Formation fractured rock aquifer.


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NC-3.4 Groundwater modelling results

The paucity of data prevents any quantitative assessment of the groundwater processes in this region.

NC-3.5 Rainfall-runoff modelling results

In this section the term runoff is the sum of overland flow, interflow and baseflow. It is equivalent to streamflow expressed

as a mm depth equivalent. All plots show data averaged over the modelled subcatchments of the Northern Coral region.

For this reason rainfall reported in this section may vary slightly from that reported elsewhere due to differences between

the catchment boundaries (shown in Figure NC-1) and the DEM-derived catchment boundaries used here. In this section,

where annual data are reported years are represented by numbers 1 through 77. Consistently throughout this report,

annual data are based on the water year (1 September to 31 August) and the dry season is defined as 1 May to

31 October. Unless stated otherwise scenarios Cwet, Cmid and Cdry are selected on the basis of the ranked mean

annual runoff. For more details on methods refer to Section 2.2 of the division-level Chapter 2.

NC-3.5.1 Regional synopsis

The rainfall-runoff modelling estimates runoff in 0.05 degree grid cells in 54 subcatchments (Figure NC-26). Optimised

parameter values from 14 calibration catchments are used. Thirteen of these calibration catchments are in the Northern

Coral region and one is in the adjacent Western Cape region. The majority of the calibration catchments are located in

the southern part of the region.


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Figure NC-26 Map of the modelling subcatchments, calibration catchments and calibration gauging stations used for the Northern Coral

region with inset highlighting (in red) the extent of the calibration catchments

NC-3.5.2 Model calibration

Figure NC-27 compares the modelled and observed monthly runoff and the modelled and observed daily flow

exceedance curves for the 14 calibration catchments. Nash-Sutcliffe efficiency (NSE) values provide a quantitative

measure of how well simulated values match observed values. NSE values are described in more detail in Section 2.2.3

of the division-level Chapter 2. On the monthly plots NSE is the monthly Nash-Sutcliffe efficiency value and NSE (dry

season) is the dry season monthly Nash-Sutcliffe efficiency value. On the daily flow exceedance plots, NSE is the daily

flow exceedance curve Nash-Sutcliffe efficiency value and NSE (50 to 100 percent) is the lower half of the daily flow

exeedance curve Nash-Sutcliffe efficiency value.

The results indicate that the ensemble calibration of the rainfall-runoff models Sacramento and IhacresClassic can

reasonably reproduce the observed monthly runoff series (NSE values generally greater than 0.8) and the daily flow

exceedance curve (NSE values generally greater than 0.9). The volumetric constraint used in the model calibration also

ensures that the total modelled runoff is within 5 percent of the total observed runoff.


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The calibration method places more importance on the simulation of high runoff, and therefore rainfall-runoff modelling of

the medium and high runoff is considerably better than the modelling of low runoff. It should be noted, however, that

while the relative difference between the observed and simulated low flow values may be large (which is what gives rise

to the low monthly dry season NSE values for example), the absolute difference between the observed and simulated

low flow values is generally small because both values are small. Nevertheless, an optimisation to reduce overall error

variance can result in some underestimation of high runoff and overestimation of low runoff. This is evident in some of

the scatter plots comparing the modelled and observed monthly runoff and many of the daily flow exceedance curves.

For the majority of calibration catchments the disagreement between the modelled and observed daily runoff

characteristics is discernable for runoff that is exceeded less than 1 percent of the time. This is accentuated in the plots

because of the linear scale on the y-axis and normal probability scale on the x-axis. In any case, the volumetric

constraint used in the model calibration ensures that the total modelled runoff is always within 5 percent of the total

observed runoff. As indicated by the relatively low NSE values for the lower half of the daily flow exceedance curve and

monthly dry season there may be considerable disagreement between observed and modelled low flow values (i.e.

cease-to-flow). Overall the monthly NSE values are considered sufficient for the general purposes of estimating long-

term mean annual runoff.


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Figure NC-27. Modelled and observed monthly runoff and daily flow exceedance curve for each calibration catchment in the Northern

Coral region. (Red text denotes catchments located outside the region; blue text denotes catchments used for streamflow modelling

only)

NC-3.5.3 Under historical climate

Figure NC-28 shows the spatial distribution of mean annual rainfall and runoff under Scenario A (averaged over 1930 to

2007) across the Northern Coral region. Figure NC-29 shows the mean annual rainfall and runoff averaged over the

region.

The mean annual rainfall and runoff averaged over the Northern Coral region are 1311 mm and 373 mm respectively.

The mean wet season and dry season runoff averaged over the Northern Coral region are 333 mm and 40 mm

respectively.

In this project, all runoff grids are presented as long-term mean annual values. However the distribution of monthly and

annual runoff data in northern Australia can be highly skewed; consequently the median and additional percentile values

spatially averaged over the region are also reported. The 10th percentile, median and 90th percentile annual runoff values

across the Northern Coral region are 616, 348 and 159 mm respectively. The median wet season and dry season runoff

averaged over the Northern Coral region are 317 mm and 38 mm respectively.

The mean annual rainfall varies from over 2500 mm in the south to less than 1000 mm in the Normanby catchment. The

mean annual runoff varies from over 1500 mm in some subcatchment draining the escarpments north of Cairns to

slightly more than 80 mm in the upper reaches of the Normanby catchment (Figure NC-28). Because the SILO grids

appears to under estimate rainfall inputs along these coastal escarpments runoff coefficients are uncertain. However it is

likely they exceed 50 percent of rainfall. In the upper reaches of the Normanby catchment runoff coefficients are as low


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as 10 percent of rainfall. The majority of rainfall and runoff occurs during the wet season months of December to April

(Figure NC-30). Rainfall and runoff can vary considerably from year to year with long periods over several years or

decades that are considerably wetter or drier than others (Figure NC-29). The coefficient of variation of annual rainfall

and runoff averaged over the Northern Coral region are 0.23 and 0.49.

The Northern Coral is one of 13 regions which cover the three divisions studied in this project. Mean annual rainfall and

runoff, as well as coefficients of variation, have been calculated for all of these 13 regions, and it is useful to compare the

Northern Coral results to results across all 13 regions. Across all 13 regions in this project 10th percentile, median and

90th percentile values are 1371, 936 and 595 mm respectively for mean annual rainfall and 374, 153 and 78 mm

respectively for mean annual runoff. The mean annual rainfall (1311 mm) and runoff (373 mm) averaged over the

Northern Coral region fall in the upper end of this range. Across all 13 regions in this project the 10th percentile, median

and 90th percentile values are 0.34, 0.26 and 0.19 respectively for the coefficient of variation of annual rainfall and 1.39,

0.69 and 0.48 for the coefficient of variation of runoff. The coefficients of variation of annual rainfall (0.23) and runoff

(0.49) averaged over the Northern Coral region are among the lowest of the 13 reporting regions.

(a) (b)

Figure NC-28. Spatial distribution of mean annual (a) rainfall and (b) modelled runoff across the Northern Coral region under Scenario A

(a) (b)

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Figure NC-29. Mean annual (a) rainfall and (b) modelled runoff in the Northern Coral region under Scenario A

Figure NC-30(a,b) shows the minimum and maximum monthly rainfall and runoff and the range of values between the

25th and 75th percentile monthly rainfall and runoff. Figure NC-30(c,d) shows the mean and median monthly flows and the

range of values between the 25th and 75th percentile monthly rainfall and runoff.


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mm

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A range

A mean

A median

Figure NC-30. Minimum, maximum and A range monthly (a) rainfall and (b) modelled runoff; and mean, median and A range monthly (c)

rainfall and (d) modelled runoff in the Northern Coral region under Scenario A (A range is the 25th to 75th percentile monthly rainfall or

runoff)

NC-3.5.4 Under recent climate

The mean annual rainfall and runoff under Scenario B (1996 to 2007) are 8 percent and 19 percent higher respectively

than the historical (1930 to 2007) mean values. The spatial distribution of rainfall and runoff across the Northern Coral

region under Scenario B is shown in Figure NC-31.


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Figure NC-31. Spatial distribution of mean annual (a) rainfall and (b)modelled runoff across the Northern Coral region under Scenario B

NC-3.5.5 Under future climate

Figure NC-32 shows the percentage change in the mean annual runoff averaged over the Northern Coral region under

Scenario C relative to Scenario A for the 45 scenarios (15 global climate models (GCMs) for each of the high, medium

and low global warming scenarios). The percentage change in the mean annual runoff and rainfall from the

corresponding GCMs are also tabulated in Table NC-7.

The figure and table indicate that the potential impact of climate change on runoff can be very significant. Although there

is considerable uncertainty in the estimates, the results indicate that runoff in ~2030 in the Northern Coral region is more

likely to increase than decrease. Rainfall-runoff modelling with climate change projections from nine of the GCMs shows

an increase in mean annual runoff, while rainfall-runoff modelling with climate change projections from six of the GCMs

shows a decrease in mean annual runoff. The wide range of mean annual runoff values shown in Figure NC-32 and

Table NC-7 is primarily due to the wide range of future projections of rainfall by the 15 GCMs.

Because of the large variation between GCM simulations and the method used to obtain the climate change scenarios,

the biggest increase and biggest decrease in runoff come from the high global warming scenario. For the high global

warming scenario, rainfall-runoff modelling with climate change projections from two of the GCMs indicates a decrease in

mean annual runoff greater than 10 percent while rainfall-runoff modelling with climate change projections from two of

the GCMs indicates an increase in mean annual runoff greater than 10 percent.

In subsequent reporting here and in other sections, only results from an extreme ‘wet’, ‘mid’ and extreme ‘dry’ variant are

shown (referred to as scenarios Cwet, Cmid and Cdry). Under Scenario Cwet, results from the second highest increase

in mean annual runoff from the high global warming scenario are used. Under Scenario Cdry, results from the second

highest reduction in mean annual runoff from the high global warming scenario are used. Under Scenario Cmid, the

median mean annual runoff results from the medium global warming scenario are used. These are shown in bold in

Table NC-7.

Under scenarios Cwet, Cmid and Cdry, mean annual runoff increases by 36 and 1 percent and decreases by 19 percent

relative to Scenario A. By comparison, the range based on the low global warming scenario is a 19 to -11 percent

change in mean annual runoff. Figure NC-33 shows the mean annual runoff across the Northern Coral region under

scenarios A and C. The linear discontinuities that are evident in Figure NC-33 are due to GCM grid cell boundaries.


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-40

-20

0

20

40

60

mri

csiro

giss

_aom

miro

cm

pi

inm

cmcn

rm iap

ipsl

ncar

_pcm

ncar

_ccsm gf

dlm

iub

cccm

a_t6

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cccm

a_t4

7

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High global warming

Medium global warming

Low global warming

Figure NC-32. Percentage change in mean annual runoff under the 45 Scenario C simulations (15 global climate models and three

global warming scenarios) relative to Scenario A

Table NC-7. Summary results under the 45 Scenario C simulations for the modelled subcatchments in the Northern Coral region

(numbers show percentage change in mean annual rainfall and runoff under Scenario C relative to Scenario A)

High global warming Medium global warming Low global warming

GCM Rainfall Runoff GCM Rainfall Runoff GCM Rainfall Runoff

mri -9% -23% mri -7% -18% mri -5% -13%

csiro -10% -19% csiro -8% -15% csiro -5% -11%

giss_aom -2% -8% giss_aom -1% -6% giss_aom -1% -4%

miroc -1% -6% miroc 0% -5% miroc 0% -4%

mpi -2% -5% mpi -2% -4% mpi -1% -3%

inmcm 1% -3% inmcm 1% -2% inmcm 1% -2%

cnrm 2% 2% cnrm 1% 1% cnrm 1% 1%

iap 1% 2% iap 1% 1% iap 0% 1%

ipsl 2% 3% ipsl 1% 2% ipsl 1% 2%

ncar_pcm 2% 4% ncar_pcm 2% 3% ncar_pcm 1% 2%

ncar_ccsm 3% 4% ncar_ccsm 2% 3% ncar_ccsm 2% 2%

gfdl -1% 7% gfdl 0% 5% gfdl 0% 3%

miub 2% 8% miub 2% 6% miub 1% 4%




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Figure NC-33. Spatial distribution of mean annual rainfall and modelled runoff across the Northern Coral region under Scenario A and

under Scenario C relative to Scenario A


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NC-3.5.6 Summary results for all scenarios

Table NC-8 shows the mean annual rainfall, runoff and actual evapotranspiration under Scenario A averaged over the

Northern Coral region, and the percentage changes in the rainfall, runoff and actual evapotranspiration under scenarios

B and C relative to Scenario A. The Cwet, Cmid and Cdry results are based on the mean annual runoff, and the rainfall

changes shown in Table NC-8 are the changes in the mean annual value of the rainfall series used to obtain the runoff

under scenarios Cwet, Cmid and Cdry. The changes in mean annual rainfall do not necessarily translate directly to the

changes in mean annual runoff because of changes in seasonal and daily rainfall distributions and the relationship

between rainfall and runoff is non-linear. The latter factor usually results in small changes in rainfall to be amplified in

runoff (Table NC-7).

Figure NC-34 shows the mean monthly rainfall and runoff under scenarios A and C averaged over the 77 years for the

region. Figure NC-35 shows the daily rainfall and flow exceedance curves under scenarios A and C averaged over the

region. In Figure NC-34 Cwet, Cmid and Cdry are selected on a month-by-month basis, while in Figure NC-35 Cwet,

Cmid and Cdry are selected for every day of the daily flow exceedance curve.

Table NC-8. Water balance over the entire Northern Coral region under Scenario A and under scenarios B and C relative to Scenario A

Scenario Rainfall Runoff Evapotranspiration

mm

A 1311 373 938

percent change from Scenario A

B 8% 19% 4%

Cwet 13% 36% 3%

Cmid 1% 1% 0%

Cdry -10% -19% -7%

(a) (b)

0

60

120

180

240

300

360


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0

30

60

90

120

150

180


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Cmid

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Figure NC-34. Mean monthly (a) rainfall and (b) modelled runoff in the Northern Coral region under scenarios A and C. (C range is

based on the consideration of each month separately – the lower and upper limits in C range are therefore not the same as scenarios

Cdry and Cwet)


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0

15

30

45

60

0% 25% 50% 75%Percent of time equalled or exceeded

Dai

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all (

mm

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. C rangeCmidBA

0

5

10

15

20

0% 25% 50% 75%Percent of time equalled or exceeded

Dai

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unof

fl (m

m) ... C range

CmidBA

Figure NC-35. Daily flow exceedance curves for (a) rainfall and (b) modelled runoff in the Northern Coral region under scenarios A, B

and C. (C range is based on the consideration of each month separately – the lower and upper limits in C range are therefore not the

same as scenarios Cdry and Cwet)


The rainfall-runoff model verification analysis with data from 123 catchments from across all of northern Australia

indicates that the mean annual runoff for ungauged catchments are under estimated or over estimated, when using

optimised parameter values from a nearby catchment, by less than 20 percent in 40 percent of catchments and by less

than 50 percent in 80 percent of the catchments.

The level of confidence of the runoff estimates for the Northern Coral region is variable depending on the locations of the

gauged catchments from which the rainfall-runoff model is calibrated against and the uncertainty in rainfall inputs along

the steep coastal escarpments north of Cairns. Transposing parameters sets in the Northern Coral region is problematic,

particularly in the northern half of the region where the distances between donor and target subcatchments are large.

Diagrams in Petheram et al. (2009) illustrate which calibrated rainfall-runoff model parameter sets are used to model

streamflow in the ungauged subcatchments in the Northern Coral region.

The undefined coastal regions of the Northern Coral region cover a relatively small area, but constitute a large area

relative to the area of the region. The level of confidence in modelling these regions is low. Figure NC-36 shows the level

of confidence in the modelling of the mid to high runoff events (i.e. peak flows) and dry season runoff for the

subcatchments of the Northern Coral region. It should be noted that these maps of level of confidence are not statistical

confidence levels and are intended to only convey a broad reliability of prediction. The level of confidence in streamflow

predictions will vary slightly from the predictions for runoff shown below as discussed in Section 2.2.6 of the division-level

Chapter 2.

There is a high degree of confidence that dry season runoff in the Northern Coral region is low because it is known that

rainfall and baseflow are low during the dry season. The map of level of confidence for dry season flow shown in Figure

NC-36 provides a relative indication of how well dry season metrics, such as the cease-to-flow criteria, are simulated.

Although there is uncertainty associated with annual runoff volumes for individual ungauged catchments in the Northern

Coral region, they are not all biased to one direction. The non-systematic errors therefore tend to cancel one another to

some extent, and across the entire Northern Coral region the long-term average monthly and annual results are

reasonable. As shown in Figure NC-36, in many areas of the Northern Coral region localised studies will require more

detailed analysis than undertaken and reported here and would most likely require the site to be visited and additional

field measurements made.


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Figure NC-36. Level of confidence in the modelling of runoff for (a) mid- to high flow events and (b) monthly dry season flow events for

the modelling subcatchments of the Northern Coral region. 1 is the highest level of confidence, 5 is the lowest

NC-3.6 River system water balance

NC-3.6.1 River model configuration

The Northern Coral region is comprised of nine AWRC river basins and has an area of 46,551 km2. Under the historical

climate the mean annual runoff across the region is 373 mm (Section NC-3.5.3), which equates to a mean annual

streamflow across the region of 17,364 GL.

No information on infrastructure, water demand, water management, sharing rules or future development were available,

and consequently there is no river modelling section to the Northern Coral region report. Streamflow time series have

been generated for each streamflow reporting node (SRN) based on the upstream grid cell rainfall-runoff simulations, as

described in Section 2.2.5 of the division-level Chapter 2. The locations of these nodes are shown in Figure NC-37.

Summary streamflow statistics for each SRN are reported in Petheram et al. (2009). In addition to the streamflow time

series generated by the rainfall-runoff models, a range of hydrological metrics computed using multiple regression

analysis are also available for each SRN (as described in Section 2.2.7 of the division-level Chapter 2). The complete set

of results for the multiple regression analysis is reported in SKM (2009). The merit of each approach is discussed in

Section 2.2.7 of the division-level Chapter 2.


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Figure NC-37. Location of streamflow reporting nodes (guaging stations, environmental sites, dummy nodes and storage inflows) in the

Northern Coral region

NC-3.7 Changes to flow regimes at environmental assets

Section 1.3 of the division-level Chapter 1 describes how environmental assets were shortlisted for assessment by this

project. Five environmental assets have been shortlisted in the Northern Coral region: Lloyd Bay, Lower Daintree River,

Marina Plains – Lakefield Aggregation, Newcastle Bay – Escape River Estuarine Complex, and Oliver River. The

locations of these assets are shown in Figure NC-1 and the assets are characterised in Chapter NC-2.

This section presents the assessment of these shortlisted assets and reports metrics for those assets which have

sufficient confidence in the modelled streamflow to enable analysis. Confidence in results for low flows and high flows

was calculated separately on a scale of 1 to 5, with 1 indicating results with the highest confidence (as described in

Section 2.2.6 of the division-level Chapter 2). Hydrological regime metrics (as defined in Section 2.5 of the division-level

Chapter 2) for either low flows or high flows are reported only where confidence levels are 1, 2 or 3. If confidence levels

in the low flows or high flows are ranked 4 or 5, results are not reported and are labelled NR (not reported).


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Some of the assets in this region have multiple nodes at which streamflow modelling results are available. When

reporting hydrological regime metrics for such assets a single node was selected. The selected node was that with the

highest streamflow confidence level and the largest proportion of streamflow to the asset. Results for all nodes are

presented in McJannet et al. (2009). In the absence of site-specific metrics for the Northern Coral region a set of

standardised metrics related to high and low flows have been utilised. However the conversion of these metrics into

environmental impacts still requires development of quantitative relationships between flow and ecology.

NC-3.7.1 Standard metrics

Table NC-9. Standard metrics for changes to surface water flow regime at environmental assets in the Northern Coral region

Standard metrics Units A B Cwet Cmid Cdry Dwet Dmid Ddry

change from Scenario A

Lloyd Bay - Node 1 (confidence level: low flow = 4, high flow = 3)

Annual flow (mean) GL 348 +29% +34% 0% -18% nm nm nm

Wet season flow (mean)* GL 319 +30% +35% 0% -19% nm nm nm

Dry season flow (mean)** GL NR NR NR NR NR nm nm nm

Low flow threshold (discharge exceeded 90% of the time in Scenario A)

GL/d NR

Number of days below low flow threshold (mean) d/y NR NR NR NR NR nm nm nm

Number of days of zero flow (mean) d/y NR NR NR NR NR nm nm nm

High flow threshold (discharge exceeded 5% of the time in Scenario A)

GL/d 4.84

Number of days above high flow threshold (mean) d/y 18.3 +8.3 +5.6 +0.1 -4.3 nm nm nm

Lower Daintree River - Node 1 (confidence level: low flow = 3, high flow = 3)

Annual flow (mean) GL 1120 +6% +15% -3% -25% nm nm nm

Wet season flow (mean)* GL 885 +9% +17% -2% -26% nm nm nm

Dry season flow (mean)** GL 236 -6% +9% -5% -25% nm nm nm


GL/d 0.276

Number of days below low flow threshold (mean) d/y 36.5 +3.3 -2.5 -1.4 +31.4 nm nm nm

Number of days of zero flow (mean) d/y 0 0 0 0 0 nm nm nm


GL/d 11

Number of days above high flow threshold (mean) d/y 18.3 +1.9 +3.3 -0.5 -6 nm nm nm

Marina Plains - Lakefield Aggregation - Node 4 (confidence level: low flow = 3, high flow = 3)

Annual flow (mean) GL 1410 0% +45% -6% -31% nm nm nm

Wet season flow (mean)* GL 1370 -1% +46% -6% -31% nm nm nm

Dry season flow (mean)** GL 38.2 +27% +27% -13% -34% nm nm nm


GL/d 0.00587

Number of days below low flow threshold (mean) d/y 36.5 +6.9 -14.1 +1.8 +24.9 nm nm nm

Number of days of zero flow (mean) d/y 0 0 0 0 +0.5 nm nm nm


GL/d 21.9

Number of days above high flow threshold (mean) d/y 18.3 -0.7 +6.8 -0.8 -6.4 nm nm nm

Olive River - Node 1 (confidence level: low flow = 4, high flow = 3)

Annual flow (mean) GL 840 +14% +32% 0% -19% nm nm nm

Wet season flow (mean)* GL 760 +14% +33% 0% -20% nm nm nm

Dry season flow (mean)** GL NR NR NR NR NR nm nm nm


GL/d NR

Number of days below low flow threshold (mean) d/y NR NR NR NR NR nm nm nm

Number of days of zero flow (mean) d/y NR NR NR NR NR nm nm nm


GL/d 11.9

Number of days above high flow threshold (mean) d/y 18.3 +2.3 +7.8 +0.1 -5.4 nm nm nm

*Wet season covers the six months from November to April; ** Dry season covers the six months from May to October. NR – metrics not reported because streamflow confidence level is ranked 4 or 5; nm – not modelled


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Lloyd Bay

The surface water flow confidence level for the selected reporting node for Lloyd Bay (see location on Figure NC-8) is

considered moderately reliable (3) for wet season flows and unreliable (4) for dry season flows (Table NC-9). Under

Scenario A annual flow into this asset is dominated by wet season flows (92 percent) which have been 30 percent higher

under Scenario B. Annual and seasonal flows do not change under Scenario Cmid when compared to Scenario A, but

there are large increases under Scenario Cwet (34 to 35 percent) and moderate decreases under Scenario Cdry (18 to

19 percent). There are no development Scenarios for the area upstream of this asset.

In Scenario B the high flow threshold exceedance has been more frequent than under Scenario A (Table NC-9). There is

little change in high flow threshold exceedance under Scenario Cmid when compared to Scenario A. Under Scenario

Cwet high flow exceedance increases moderately from Scenario A; conversely, there is a more moderate decrease in

high flow days under the Scenario Cdry. There are no low flow metrics reported for this asset.

Lower Daintree River

The surface water flow confidence level for the selected reporting node for the Lower Daintree River (see location on

Figure NC-9) is considered moderately reliable (3) for both wet season flows and dry season flows (Table NC-9). Under

Scenario A annual flow into this asset is dominated by wet season flows (79 percent) which have been 9 percent higher

under Scenario B. Dry season flows are 6 percent lower under Scenario B when compared to Scenario A. Annual and

seasonal flows do not change much under Scenario Cmid when compared to Scenario A, but there are moderate

increases under Scenario Cwet (9 to 17 percent) and moderate decreases under Scenario Cdry (25 to 26 percent).

There are no development scenarios for the area upstream of this asset.

Compared to Scenario A, the number of days when flow is less than the low flow threshold does not change very much

under Scenarios Cmid or Cwet, but there is a very large increase in low flow days under Scenario Cdry (Table NC-9).

There were no zero flow days at this asset. Under Scenario B the high flow threshold exceedance has been more

frequent than in Scenario A. There is little change in high flow threshold exceedance under Scenario Cmid. Under

Scenario Cwet high flow exceedance increases moderately from Scenario A; conversely, there is a large decrease in

high flow days under the Scenario Cdry.

Marina Plains Lakefield Aggregation

The surface water flow confidence level for the selected reporting node for the Marina Plains Lakefield Aggregation (see

location on Figure NC-10) is considered moderately reliable (3) for both wet season flows and dry season flows (Table

NC-9). Under Scenario A annual flow into this asset is dominated by wet season flows (97 percent) which have been

1 percent lower under Scenario B. Conversely dry season flows were 27 percent higher under Scenario B than under

Scenario A. Annual and seasonal flows change somewhat under Scenario Cmid when compared to Scenario A, but

there are large increases under Scenario Cwet (27 to 46 percent) and large decreases under Scenario Cdry (31 to

34 percent). There are no development scenarios for the area upstream of this asset.

Compared to Scenario A, the number of days when flow is less than the low flow threshold does not change very much

under Scenarios Cmid, but there is a very large increase in low flow days under Scenario Cdry and also a large decrease

in low flow days under Scenario Cwet (Table NC-9). There were no zero flow days at this asset, except for Scenario Cdry

which had a small increase in zero flow days. Under Scenario B the high flow threshold exceedance has been less

frequent than under Scenario A. There is little change in high flow threshold exceedance under Scenario Cmid. Under

Scenario Cwet there is a large increase in high flow exceedance from Scenario A; conversely, there is a large decrease

in high flow days under the Scenario Cdry.

Newcastle Bay – Escape River Estuarine Complex

The surface water flow confidence levels for both high and low flows for all nodes within the Newcastle Bay – Escape

River Estuarine Complex are ranked unreliable (4 or 5) therefore they are of insufficient quality to allow environmental

flow metrics to be calculated.


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Olive River

The surface water flow confidence level for the selected reporting node for the Olive River (see location on Figure NC-

12) is considered moderately reliable (3) for wet season flows and unreliable (4) for dry season flows (Table NC-9).

Under Scenario A annual flow into this asset is dominated by wet season flows (90 percent) which have been 14 percent

higher under Scenario B. Annual and seasonal flows do not change under Scenario Cmid when compared to Scenario A,

but there are large increases under Scenario Cwet (32 to 33 percent) and moderate decreases under Scenario Cdry

(19 to 20 percent). There are no development scenarios for the area upstream of this asset.

Under Scenario B the high flow threshold exceedance has been more frequent than under Scenario A. There is little

change in high flow threshold exceedance under Scenario Cmid. Under Scenario Cwet there is a large increase in high

flow exceedance from Scenario A; conversely, there is a moderate decrease in high flow days under Scenario Cdry.

There are no low flow metrics reported for this asset.


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NC-3.8 References

Crosbie RS, McCallum JL, Walker GR and Chiew FHS (2008) Diffuse groundwater recharge modelling across the Murray-Darling basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. 108pp.

Crosbie RS, McCallum JL and Harrington GA (2009) Diffuse groundwater recharge modelling across Northern Australia. A report to the Australian Government from the CSIRO Northern Australian Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, CSIRO, Australia. In prep.

Horn AM, Derrington EA, Herbert GC, Lait RW and Hillier JR (1995) Groundwater Resources of Cape York Peninsula. Strategy office of the co-ordinator general of Queensland, Brisbane, Department of the Environment, Sport and Territories, Canberra, Queensland Department of Primary Industries, Brisbane and Mareeba, and Australian Geological Survey Organisation, Mareeba.

Petheram C, Rustomji P and Vleeshouwer J (2009) Rainfall-runoff modelling across northern Australia. A report to the Australian Government from the CSIRO Northern Australian Sustainable Yields Project. CSIRO Water for a Healthy Country Flagship, CSIRO, Australia. In prep.

SKM (2009) Regionalisation of hydrologic indices. Northern Australia sustainable yields. A report prepared by Sinclair Knight Merz for the CSIRO Northern Australia Sustainable Yields project. SKM, Melbourne. 183pp.

Zhang L and Dawes W (1998) WAVES - An integrated energy and water balance model. Technical Report No. 31/98, CSIRO Land and Water.

Web: www.csiro.au/flagships

For further information:

Water for a Healthy Country Flagship Project LeaderDr Richard CresswellPhone: 07 3214 2767Email: [email protected]: www.csiro.au/partnerships/NASY

Northern Australia Water Futures Assessment Department of the Environment, Water, Heritage and the Arts Phone: 02 6274 1111 Email: [email protected] Web: http://www.environment.gov.au/nawfa

About the project

The Northern Australia Sustainable Yields (NASY) Project has assessed the water resources of northern Australia. The project modelled and quantified, within the limits of available data, the changes to water resources under four scenarios: historical climate; recent climate; future climate considering current water use and future climate with potential future water demand. The project identified regions that may come under increased, or decreased, stress due to climate change and increased water use.

The assessments made in this project provide key information for further investigations carried out through the Australian Government’s Northern Australia Water Futures Assessment. This initiative aims to develop a knowledge base so that any development proceeds in an ecologically, culturally and economically sustainable way.

The NASY project was commissioned by the National Water Commission in consultation with the Australian Government Department of the Environment, Water, Heritage and the Arts. This followed a March 2008 agreement by the Council of Australian Governments to undertake comprehensive scientific assessments of water yield in all major water systems across the country and provide a consistent analytical framework for water policy decisions across the nation. CSIRO is also undertaking assessments in south-west Western Australia and Tasmania.

The NASY project was reviewed by a Steering Committee and a Technical Reference Panel. Both include representation from federal and state governments, as well as independent experts.

Documents

Water in the Northern Coral region of the Northern North