Macquarie River Broadwater Ecosystems Assessmentdpipwe.tas.gov.au/Documents/Forum June...
Transcript of Macquarie River Broadwater Ecosystems Assessmentdpipwe.tas.gov.au/Documents/Forum June...
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.