Drain C, southwest from Bool Lagoon
2009 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2009.
- Likely to be at least moderately enriched with nutrients when wet due to the surrounding land uses.
- Riparian vegetation narrow but consists of native trees over weeds and grasses.
About the location
Drain C is a moderately sized drain in the South East with a catchment area of about 250 km2. It rises at an elevation about 60 metres above sea level near Coonawarra and flows in a westerly direction into Drain M, ultimately discharging into Lake George at Beachport.
Drain C is an artificially constructed drain where the primary function is to remove surface water and draining saline groundwater to improve agricultural productivity in the region (Department for Water 2010). Given its artificial character, the drain is not expected to be in a highly rated aquatic ecosystem condition, although it does provide significant habitat for many aquatic species in the region.
The major land uses are vineyards, grazing and cropping, with some native vegetation present in the catchment. The monitoring site was located near Coles Killanoola Road, about 8.5 km southwest of Bool Lagoon Game Reserve and 22 km west of Coonawarra.
The drain was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure and some changes to the way the ecosystem functions. The lack of shading and filtering functions provided by the limited vegetated riparian zone were used to assess this site as fair, as there is likely to be at least moderate enrichment effects when water is present in the drain.
The drain was dry when inspected in autumn and spring 2009 so macroinvertebrate and water chemistry data were not collected from this site.
The sediment was dominated by sand; samples taken from below the surface were well aerated.
There were no aquatic plants growing in the channel or on the water’s edge. The invasion by introduced grasses such as Canary Grass (Phalaris)and other terrestrial weeds indicates that the drain has been dry for a long time.
The riparian zone was narrow and consisted of a few eucalypt trees over introduced grasses and thistles. The surrounding vegetation at the site was native woodland.
Special environmental features
The extent of native woodland surrounding the drain was notable for the region.
Pressures and management responses
|Drought||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.|
|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.|
|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 does not impede access for management and maintenance.|