Reedy Creek–K Drain, between Robe and Lucindale
2009 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2009.
- Likely that the drain would be enriched with nutrients when wet due to the surrounding land uses.
- Riparian vegetation limited to only introduced grasses.
- Large deposit of silt in the middle of the channel.
About the location
Reedy Creek-K Drain is a small drain in the lower South East with a catchment area of over 50 square kilometres. It rises between the West Avenue Range and Reedy Creek Range just north of the Reedy Creek-Wilmot Drain, flows in a northerly direction to join with Avenue Flat-K Drain and then discharges into the upper reaches of Drain L. The major land use is grazing.
Reedy Creek-K Drain 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 monitoring site was located on Old Robe Road, about 28 kilometres west-south-west of Lucindale.
The drain was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance, including poor riparian habitat and large deposits of fine sediment in the channel.
The drain was dry in autumn and too shallow to sample in spring 2009, so macroinvertebrate data were not available for the site inspected.
One of the shallow pools present in spring was analysed for general water characteristics and assessed as moderately fresh (salinity 1,525 mg/L), well oxygenated (134% saturation), clear, and with moderate to high concentrations of nutrients such as nitrogen (5.21 mg/L) and phosphorus (0.07 mg/L).
The sediments were dominated by algae, detritus, silt and clay; samples taken from below the surface were aerobic but would be expected to become anaerobic when wet due to the large organic load in the sediments. A large deposit of fine silt was recorded from the middle of the channel.
A range of submerged (Ruppia or Stuckenia) and emergent plants (Cyperus, Juncus, introduced Rorippa and Schoenoplectus) was growing in the channel and on the water’s edge. These plants covered between 10-35% of the channel and an even larger area of between 65%-90% was covered by large growths of filamentous green algae.
The narrow riparian zone lacked any trees or shrubs and was only vegetated by introduced grasses. The surrounding vegetation at the site was cropping land and grassland.
Special environmental features
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 1860’s 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 doesn’t impede access for management and maintenance.|