Drain B, near Penola Conservation Park
2009 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2009.
- Likely to be enriched with nutrients when wet due to the surrounding land uses.
- Riparian vegetation limited to a few gum trees over introduced grasses.
About the location
Drain B is a moderately sized drain in the South East with a catchment area over 120 km2. It rises at an elevation about 60 metres above sea level near Penola, receives drainage from some minor unnamed drains in the region, and flows in a westerly direction into Baker Range Drain and then Drain M, ultimately discharging into Lake George at Beachport.
Drain B 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 grazing and forestry. The monitoring site was located on Rifle Range Road, about 15 km west of Penola.
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 a lack of vegetative cover in the riparian zone and dominance by fine sediments in the channel.
The drain was dry in autumn and spring 2009 so macroinvertebrate and water quality data were not available for this site.
The sediments were dominated by sand and detritus; samples taken from below the surface were aerobic.
There were no aquatic plants growing in the channel or on the water’s edge. The drain had obviously been dry for several years due to the invasion of the channel by terrestrial grasses and other weedy plant species. The riparian zone was narrow and consisted of a few scattered eucalypts over introduced grasses. The surrounding vegetation at the site included a Blue Gum Plantation and cleared grazing land.
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.|