Macquarie River Broadwater qEcosystems Assessment

Ch i B bbiChris BobbiDepartment of Primary Industries, Parks, Water and Environment

Background to the studyac g ou d to t e study

Previous studies conducted by IFC and DPIF in the mid-1990 11990s1.

Collected a considerable amount of data on the habitat and ecology of broadwaters at Morningside and Barton.

The study was conducted at a time when the river was yexperiencing relatively healthy and consistent flows and was not under the same level of water use pressure.

1 Davies and Humphries (1996)

5000

4000

4500

3000

3500

1500

2000

2500

500

1000

1980 1990 20000

Period(01/01/1980 @ 00:00:00 to 01/01/2009 @ 00:00:00)

Mean monthly flow (ML d 1) for Macquarie d/s Elizabeth (black) andMean monthly flow (ML d-1) for Macquarie d/s Elizabeth (black) and Macquarie at Trefusis (red)

B t

The largest is more than 200m wide and over 25m deep

Barton

wide and over 25m deep.

Typically, broadwaters are h ll d b Morningsideshallower and can be

more than 1 km in length.

Morningside

Morningside Bridge

Broadwaters used as water extraction points for agriculture and have also been important areas for trout fishing based on mayfly and caddisfly hatches.

Important environmental attributesp

Fringing aquatic plant communities important as:

- hotspot of plant diversity

- habitat for aquatic invertebrates and native fish

- high potential for processing nutrient inputs

Aims of the broadwater assessment

1. To replicate the macroinvertebrate sampling that was done in the early 1990’s so as to characterise anydone in the early 1990 s so as to characterise any changes that might have occurred during the intervening period.

2. To undertake instream and riparian vegetation assessments to better understand the composition and condition of communities that currently existcondition of communities that currently exist.

3. Conduct simple water flux measurements to assess the degree of connectedness of surface water and local ggroundwater systems.

Barton*-Macroinvertebrates-Vegetation-Seepage measurements

Morningside-Macroinvertebrates-VegetationVegetation

*Mt Morriston*-Vegetation

* Sites also used for E-flow assessment

* - Indicates sites where environmental flow assessments were also conducted.

Vegetation assessmentsg

• species/community presence

• perpendicular belt transects

Sampling benthic macroinvertebratesp g

Edgewater sampling from broadwater pools

Riffle sampling

Results: VegetationVegetation types and their requirements

g

1. River Channel Vegetation Communities- Three communities identified (TASVEG: AHF, ASF and AHL)

- Appear to have adequate water supply to maintain them.

2 Floodplain Vegetation Communities2. Floodplain Vegetation Communities- Two grassland, one riparian scrub and Eucalyptus ovata

forest communitiesforest communities

- Gradient of plant species across the floodplain. - Further away from the river introduced terrestrial species areFurther away from the river, introduced terrestrial species are dominant, reflecting the lack of wetting flows in recent years.

Macroinvertebrates

Amphipoda (shrimp)Mollusca (snails)EphemeropteraOdonata Amphipoda (shrimp)( )(mayflies)

Odonata(dragonflies)

Coleoptera (beetles)

Diptera

Oligochaeta (worms)

Diptera(true flies)

Trichoptera (caddis)

Results: Macroinvertebrates

0%

Morningside 1990s Morningside 2008

Amphipoda

12%

6%20%

Amphipoda

Coleoptera

Diptera

Ephemeroptera

15% 0%30%

Amphipoda

Coleoptera

Diptera

Ephemeroptera

d

38%5%

1%

18% Odonata

Trichoptera

Mollusca

Oligocheata

33%

6%

2%

6%

8%

Odonata

Trichoptera

Mollusca

Oligocheata

1%

Barton 1990s

Amphipoda

2%

Barton 2008

Amphipoda

29%

40%

Amphipoda

Coleoptera

Diptera

Ephemeroptera

Od

30%

15%

16%Amphipoda

Coleoptera

Diptera

Ephemeroptera

Od

4%

8%

0%

14%

Odonata

Trichoptera

Mollusca

Oligocheata

0%

31%0%1%

7%

Odonata

Trichoptera

Mollusca

Oligocheata

4%0%

Results: Macroinvertebrates

Mayflies: sensitive to environmental degradationy g

1990’s:Equal proportions of Caenid and Leptophlebiid mayfliesEqual proportions of Caenid and Leptophlebiid mayflies present at both locations.

Baetids less abundant.

2008:N L t hl biid fli t ith B tNo Leptophlebiid mayflies at either Barton or Morningside. Only Caenids present at Barton

Baetid mayflies were only present in very low numbersBaetid mayflies were only present in very low numbers at Morningside.

Results: Macroinvertebrates

1990’s Study 2008 Study

Summary: Macroinvertebrates

No substantial change in the diversity of macroinvertebrates, but large changes in the proportion of individual groups

y

but large changes in the proportion of individual groups.

Increased dominance of taxa that are tolerant of degraded habitat quality and a decline in sensitive taxahabitat quality, and a decline in sensitive taxa .

Loss of Leptophlebiid mayflies in the lower river system is most likely due to Blackman Dam rupture (siltation)most likely due to Blackman Dam rupture (siltation).

Drought has resulted in less differentiation between riffle and ‘slackwater’ (pools and edgewaters) communities, andand slackwater (pools and edgewaters) communities, and less difference between the two study reaches.

Overall ConclusionsDroughts favour agricultural and exotic weeds, and native riparian plant communities (where they persist) are impacted

Instream and fringing plant communities are relatively healthy and biodiverse

Floods are likely to be important for dispersing seed from aquatic plants to floodplain wetlands and scourpools, as well as inhibiting the abundance of exotics in the riparian zone.

While the diversity of aquatic macroinvertebrates at Barton and Morningside has not changed, there is a greater dominance of taxa that are tolerant of habitat degradation (e g siltation)are tolerant of habitat degradation (e.g. siltation)

The difference between hydraulic conditions in riffles and pools is less, leading to a more homogenous aquatic invertebrate community overall.

Further information

DPIW (2009) Macquarie River Broadwater Ecosystems Assessment. Report No. WA 09/03 DPIW Hobart TasmaniaWA 09/03 DPIW, Hobart, Tasmania

Davies, P.E. and Humphries, P. (1996) An Environmental Flow Study of the Meander, Macquarie and South Esk Rivers, Tasmania. Report to DPIF, Hobart TasmaniaTasmania.

Website: www.dpiw.tas.gov.au/water

Thank-you for listening.