South East NRM Regional Summary
2009 Aquatic Ecosystem Condition Report
A total of 71 sites were sampled in the South East during autumn and spring 2009. These sites were located throughout the region from Bordertown to Port MacDonnell.
- Few naturally occurring creeks occur in the region that is dominated by artificially constructed drains which incidentally provide significant habitat for aquatic biota.
- Sites on creeks and drains near the coastline were generally in the best ecological condition whereas inland sites were in poorer condition.
- Sites receiving urban stormwater, located within heavily cleared catchments, or newly constructed drains rated the poorest in the region.
- Drought effects likely to have contributed to the generally degraded condition of the majority of sites sampled.
- Agricultural land uses contribute large loads of nutrients, salt and fine sediment to most drains and streams in the region.
- Nutrient enrichment affecting most creeks and drains in the region as evidenced by high nutrient concentrations and large growths of filamentous algae, phytoplankton and/or aquatic plants.
- Riparian zones generally degraded or largely non-existent, apart from introduced grasses and weeds that are often grazed and damaged by stock accessing the banks.
- The most significant biodiversity hot-spots in terms of rare and sensitive macroinvertebrate species included the creeks and drains along the southern coast, east of Port MacDonnell, and the Drain L catchment.
Drought effects and naturally variable rainfall patterns across the region in 2009 resulted in 30 of the 71 sites sampled being permanently wet; of these only nine had some flowing water present in autumn and spring. Two sites had water present only in autumn, 17 were only wet in spring and 22 sites were dry during both autumn and spring.
Two sites were assessed in Good ecological condition, 24 were in Fair condition, 40 were in Poor condition, and five were in Very Poor condition.
The sites that were rated in Good condition included Benara Creek which drains into Lake Bonney SE and Piccaninnie Blue Lake Outlet which occurs within a conservation park in the southernmost part of the region. These streams were sampled from well vegetated sites and both showed only some minor indications of nutrient enrichment affecting the biological condition of each waterway.
The five sites considered to be in Very Poor condition included three from cleared agricultural areas that were dry in autumn and spring (Seymour-Robertson Drain, Drain 57 and Drain C2), one newly constructed drain (Didicoolum Drain) and a creek receiving urban stormwater (Tatiara Creek).
The sites in Poor condition were generally from areas with little remnant vegetation remaining in the landscape and ineffective riparian buffer zones. The sites rated in Fair condition included a number of creeks and drains with better developed riparian zones but still showing the effects from excessive nutrients and sediments entering each waterway.
The majority of sites sampled with water present had macroinvertebrate communities dominated by commonly occurring, tolerant species and included few rare or sensitive species. Chironomid larvae (e.g. Cricotopus, Corynoneura, Cladotanytarsus and Chironomus), corixid waterbugs, hydrobiid snails and amphipod crustaceans dominated the freshwater sites and amphipods, salt-lake snails (Coxiella) and chironomids (e.g. Procladius and Tanytarsus) were commonly recorded from the more saline sites.
The absence of substantial flowing riffle habitats in autumn and the limited number of flowing sites in spring was probably the major reason for the low number of specialised, rare and sensitive species recorded in 2009. The only sites that provided habitat for flow-dependent blackfly larvae were Avenue Flat–K Drain, Drain 44, Drain L (both from east of Lake Hawdon North and near Robe), Drain 31, Stony Creek and Piccaninnie Blue Lake Sea Outlet. The most significant sites with at least a few rare or sensitive macroinvertebrate species included Deep Creek, Eight Mile Creek, Drain L near Robe, Blackford Drain and Piccaninnie Outlet.
All creeks and drains showed at least some evidence of nutrient enrichment, including the presence of large growths of filamentous algae, high phytoplankton levels in the water, excessive growths of reeds and other aquatic plants, and/or high concentrations of nutrients. Some sites also had salinity levels well over 3,000 mg/L, which generally limits ecological communities to support the more saline tolerant types of plants and animals.
Apart from a small number of sites in national parks or ephemeral coastal streams that had intact vegetation communities, most sites had significantly disturbed riparian vegetation dominated by introduced grasses and weeds, and generally lacking any native vegetation. Many also had large areas of bare soil and showed evidence of erosion by stock accessing the banks and water directly.
Special environmental features
Few rare or sensitive species were found in the South East in 2009. Those that were collected included the freshwater crayfish (Euastacus), mayflies (Offadens, Centroptilum and Atalophlebia), caddisflies (Taschorema evansi and Lingora), blackfly larva (Austrosimulium) and a land crayfish (Geocharax). A number of sites throughout the larger drains (e.g. Drain M, Drain L, and Reedy Creek) and many smaller coastal streams and drains in the region also provide important habitat for threatened fish species such as the Southern Pygmy Perch, Yarra Pygmy Perch, Dwarf Galaxias, River Blackfish and Congolli.
Some rare and sensitive macroinvertebrate species found in the region in the past have included mayflies (Atalophlebia aurata, Ulmerophlebia pipinna, Leptoperla primitive and Nousia fuscula), stoneflies (Dinotoperla brevipennis, Dinotoperla evansi and Austrocerca tasmanica) and a beetle (Hydrophilus).
Persistent drought across much of the state since 2005 has resulted in many of the watercourses where these species occurred having limited areas of permanently flowing riffle habitats, ceasing to flow for extended periods, or drying to form only isolated pools during summer and autumn; less than ideal conditions for species that require flowing water, and good habitat and water quality for their continued survival.
This highlights the significance of the few streams and drains that have sustained regularly flowing habitats during the drought conditions that prevailed in 2009.
Pressures and management responses
The management responses in the South East NRM Region are based on the waterway being considered a drain or a creek/river.
The Drainage Network in the region supports nearly 200 regulators for water conservation and adaptive flows management practices. The freshwater weir pools of some regulators in the Lower South East are now known to support colonies of threatened aquatic species. The South Eastern Water Conservation and Drainage Board has undertaken preliminary investigations to identify additional biological hot spots in the Lower South East, and further investigations may be undertaken. This may lead to the installation of additional regulators to retain water as drought refuge at these key drain locations.
Through ground and surface water allocation planning and the South East Regional NRM Plan water affecting activity permit process the South East NRM Board seeks to manage water for environmental, social and economic purposes in a range of climatic scenarios.
|Livestock having direct access (causing sediment erosion and adding excessive nutrients).||
Drains have been constructed since the 1860s as an engineering solution to support agricultural development and it is South Eastern Water Conservation and Drainage Board practice to lease drain reserves for grazing in certain circumstances. Not all drains are subject to grazing and leases for grazing are only approved following an engineering and environmental assessment. Lease conditions require the lessee to fulfil pest plant, pest animal and CFS management requirements, thereby relieving the Board of these responsibilities.
The South East NRM Board supports targeted projects that provide opportunities for landholders to access grants for fencing for stock exclusion from time to time for priority catchments.
|Limited riparian zone vegetation (reducing habitat quality, increasing sediment erosion).||
The South Eastern Water Conservation and Drainage Board has undertaken a limited revegetation program at key locations, and has the ability to undertake further revegetation works when resources allow. Revegetation at biological hotspots is recognised as a mechanism to reduce nutrient input and soil erosion, and can be undertaken if it doesn’t impede access for management and maintenance.
The South East NRM Board assists landholders to access targeted grant opportunities for revegetation and ecosystem protection when funding is available. The Board also works closely with landholders consistent with the Board’s Regional Pest Management Plan to control weeds on their property and to assist in halting their spread to other properties.