Bakers Range Drain, west from Penola
2009 Aquatic Ecosystem Condition Report
- Dry channel with a diverse range of sediment types and patches of two types of aquatic plants.
- A small, isolated rainwater pool was present in spring but flow through the drain did not occur in 2009.
- Likely to be enriched with nutrients when wet due to the surrounding land uses.
- Riparian vegetation of weeds and grasses.
About the location
Bakers Range Drain is a large, northerly flowing drain with a catchment area of nearly 800 km2 that follows a natural watercourse along the inter-dunal flats in the South East. It rises as a series of smaller drains about 10 km east of Mount Burr and drains northwards past Lucindale where it can flow into the Water Valley wetlands during wet years.
Bakers Range 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 drainage has been modified in the past decade to allow water to be diverted into the drain from Mosquito Creek via the REFLOWS western floodway and to the West Avenue watercourse, Tilley Swamp or other locations as required for wetland watering projects as part of cross-catchment water transfers. The major land uses in the catchment include agricultural grazing and cropping, blue gum plantation forestry and minor areas of remnant native vegetation. The monitoring site was located in the mid catchment on the Robe-Penola Road, about 25 km west of Penola.
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. There was evidence of human disturbance despite the dry nature of the drain in 2009, particularly with the limited vegetative cover on the banks providing no filtering role to mitigate the movement of nutrients and fine sediment from surrounding land uses in the catchment.
The drain was dry in autumn and spring, so macroinvertebrate and water quality measurements were not available for this site. A small, temporary rainwater pool was not sampled for most parameters but field measurements indicated the water was fresh (salinity 375 mg/L) and well oxygenated (64% saturation).
The sediments were dominated by sand and detritus, with smaller amounts of silt, clay and boulder; sediment taken from below the surface was aerobic but would be expected to become anaerobic when wet, at least some of the time, due to its high organic content.
Small patches of aquatic plants or macrophytes (Schoenoplectus and Juncus) were growing in the channel, indicating that the drain probably retains water for several months during average rainfall years in the region.
The riparian vegetation lacked structure and consisted of introduced grasses, weeds, bracken and rushes. The surrounding vegetation at the site consisted of both native eucalypt woodland over bracken and sedges and Blue-gum plantation forest.
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 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.|