A grid-based model for developing regional water scenarios – applications in Europe and elsewhereFrank Farquharson

1. What is going on in Europe on topics related to “European water Scenarios” ?1. What is going on in Europe on topics related to “European water Scenarios” ?

European river flow regimes (Report to European Environment Agency), Arnell et al., 1993

The impact of Climate and other Hydrological events on European Water Supply (CHEWS), Farquharson et al, 1997 (ENV4-CT95-0138)

Estimation of Renewable water resources in the European Union (ERASM), Rees & Cole, 1997 (EUROSTAT for the European Environment Agency)

Advances in Regional Hydrology through East European Cooperation, Gustard & Cole, 1997 (ERB CIPA CT92-4018)

Groundwater and River Resources Action Programme on a European scale (GRAPES), Acreman et al, 2000 (ENV4-CT96-0186)

Assessment of the Regional Impact of Droughts in Europe (ARIDE), Demuth & Stahl (Eds), 2001 (ENV4–CT97-0553)

Establishment of a Regional Data Centre of the European Water Archive for the European territory of the former Soviet Union, 1999 (INTAS 94-4451)

European FRIEND Programme (CEH maintains a database of daily mean flows from 5000 stations from 30 countries in Europe) (UNESCO IHP)

Hydrological and hydrodynamic studies and predictions of Caspian Sea level rise; Impact of Climate and Man’s activities, Farquharson et al, 2000 (INCO-COPERNICUS IC15-CT97-0101)

Grid-based model of the Caspian Sea Basin, Meigh & Tate, 2001 (TACIS, ENVREG 9504)

Average Annual Runoff gridded at 10km x 10km

Irrigation Demand vs Average Annual Runoff

Urban Demand vs Average Annual Runoff

2. Projection of possible scenarios on a 25-50 years scale2. Projection of possible scenarios on a 25-50 years scale

Much of CEH’s experience has been restricted to impacts of climate change scenarios

However, we have also considered socio-economic factors: Changing demand Water Poverty Index Climate Vulnerability Index

The UKCIP02 Report – the ‘definitive’ source of information on probable UK climate change scenarios for impact studies

The UKCIP02 Report – the ‘definitive’ source of information on probable UK climate change scenarios for impact studies

Mean Annual rainfall over the UK – very variable !

Mean Annual rainfall over the UK – very variable !

Resolution of climate modelsResolution of climate models

Global model Regional model

300km grid 50km grid

Present day winter precipitation over BritainObserved, and simulated with RCM and GCMPresent day winter precipitation over BritainObserved, and simulated with RCM and GCM

ANNUAL

WINTER

SUMMER

Winters are getting wetter and Summers are getting drier

England & Wales Rainfall

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Predicted increase in summer temperatures (2080s compared to the present day)Predicted increase in summer temperatures (2080s compared to the present day)

Climate on islands changes very differently to the surrounding Mediterranean Sea, and can only be predicted using an RCM

Global climate model Regional climate model

A2 Scenario

How do hydrologists consider “Water Scarcity” & “Future Scenarios” ?How do hydrologists consider “Water Scarcity” & “Future Scenarios” ?

1980s and early 1990s – Too much reliance on modelling Surface Runoff• Surface runoff alone does NOT represent water

resources or availability • Models often ignored Groundwater• Took no account of DEMAND• Grid-based models used – BUT, in many cases, grids were not

linked• Runoff accumulated in grid cells – not allowed to ‘runoff’

• Grid size too coarse (constrained by data availability and computer power)

How have approaches changed ?How have approaches changed ?

Mid to late 1990s Recognition that grid must be linked to

represent river system Improved representation of groundwater Finer grid size possible due to

improvements in computers and in data availability

Recognition that DEMANDS must be built into water availability assessments

3. To address the FP6 call, there is a need for modelling at a range of scales:

3. To address the FP6 call, there is a need for modelling at a range of scales:

• A ‘Top-down’ approach of European scale modelling using Water-GAP or GWAVA• Regional or basin-scale modelling• ‘Bottom-up’ approaches

• Water Poverty Index

• Climate Vulnerability Index

GWAVA ModelGWAVA Model Global Water AVailability

Assessment

Not yet applied Globally

Developed and applied to 20

countries in Eastern and

Southern Africa (1994-98)

Applied to Volga Basin

(Russia) and Caspian Sea

basin (1999-2000) (INCO-

COPERNICUS & TACIS funding)

Also applied to 20 countries

in West Africa (2001-02) (FP5)

Studying impacts of climate

change on Bangladesh (2003-

05)

GWAVA ModelGWAVA Model

10N

20N

0N0W

10W

10E

20ET U R K E Y

I R A N

R U S S I A

U K R A IN E

I R A Q

S Y R I A

G E O R G I A

K A Z A K H S T A N

U Z B E K I S T A N

T U R K M E N I S T A N

Bla c k Se a

Ara l Se a

Ca

spia

n S ea

Vo lga

K u m a

S am ur

S afid R

ud

A trek

Kura

Terek

S u lak

Araks

Ural

Em

ba

B a k u

Te h ran

Vo lgo g rad

M o sco wO ka

M a h ab e t

Ve tlu g a

S u ra

Sta ritsaB e la ya

V iatka

S a m a ra

T b lis i

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30 Eo

65 Eo

33 No

GWAVA – General approachGWAVA – General approach 0.5 by 0.5 degree grid for both water availability and

demands (approx 50x50 kms)

Rainfall-runoff model for surface water

Groundwater availability assessed separately

Long series of climate inputs (30 years) used to estimate actual availability – now using RCM data

Linking grid cells to simulate river network

Model components to account for effects of:• lakes, reservoirs and wetlands

• abstractions and return flows

• inter-basin transfers

APPROACH – contd.APPROACH – contd.

Groundwater availability based on aquifer properties (areal extent, transmissivity, specific yield etc.) and recharge estimates

Water demands based on current and projected population and livestock numbers, information on irrigation and industrial use (i.e. socio-economic factors)

Indices of water availability versus demand derived at the grid cell scale

Rainfall-runoff model - PDMRainfall-runoff model - PDM

Moisture storage

Runoff

SUBSURFACE STORAGE

Surfacerunoff

River Flow

SURFACE STORAGE

Potential EvaporationRainfall

INPUT

OUTPUT

Baseflow

Groundwaterrecharge

Probability Distributed Moisture Storage

Does GWAVA work ?Does GWAVA work ?

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(i) Comparison of mean annual runoff

(ii) Comparison of standard deviation of annual flows

(ii) Comparison of 90% reliable dry month flows

(i) Comparison of mean annual runoff

(iii) Comparison of 90% reliable dry month flows

(ii) Comparison of standard deviation of annual flows

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Application in Caspian Sea Application in Caspian Sea BasinBasin

River inflows to the River inflows to the Caspian under climate Caspian under climate

change scenarioschange scenarios

Rainfall change for Rainfall change for 2050s based on 2050s based on

HadCM3HadCM3

Range of temperature change predictions from several climate modelling groups

Range of temperature change predictions from several climate modelling groups

Uncertainty !!Uncertainty !!

Uncertainty !!Uncertainty !!Runoff changes for 2050s estimated from 3 GCMsRunoff changes for 2050s estimated from 3 GCMs

HadCM2

CGCM1 Echam4

The flow estimation Problem in Practice – MEDIUM SCALE MODELLINGThe flow estimation Problem in Practice – MEDIUM SCALE MODELLING

Water use features

Long term gauging station

Point of interest

Medium-scale modelling -

LowFlows 2000

Medium-scale modelling -

LowFlows 2000

“Bottom-up”, Semi-qualitative approach“Bottom-up”, Semi-qualitative approach

Use techniques developed at

Wallingford by Caroline Sullivan and

Jeremy Meigh

Water Poverty Index

Climate Vulnerability Index

CONCLUSIONSCONCLUSIONS

Problems need to be tackled at a variety of scales – both in space and time

Data availability is more of a constraint than models/tools

The challenge is to bring together a range of uncertain future scenarios, derived from a variety of sources; some of which are quantified, others just quality descriptors

Natural scientists must continue to learn how to collaborate with social and economic specialists

Thank You !