Mosquito Creek Channel, west from Struan
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 introduced grasses and weeds.
- Bare banks and moderate deposits of silt in the channel.
About the location
Mosquito Creek Channel is a man-made drain in the lower South East that directs flow from Mosquito Creek into Bool Lagoon. Mosquito Creek has a large catchment area of over 1,100 km2. It rises east of Edenhope in south-western Victoria as two major branches that flow in a westerly direction and join into the one creek about nine kilometres north-east of Straun. The channel flows into Bool Lagoon about 2.5 kilometres further downstream and then flows out from the game reserve as Drain M, which flows west and eventually discharges into Lake George near Beachport. The major land uses are grazing and cropping, and the creek flows through several kilometres of the Naracoorte Caves Conservation Park just upstream from the sampling location.
Mosquito Creek Channel 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 about three kilometres downstream from the Riddoch Highway, on a track between Bool Lagoon Road and Moyhall Struan Road, about 15 kilometres south of Naracoorte.
The creek 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 in-stream and riparian habitat and indications that the channel would be nutrient enriched when wet due to the surrounding land uses.
The channel was dry in autumn and spring 2009, so macroinvertebrate and water quality data were not available for the site investigated.
The sediments were dominated by sand, clay, cobble, detritus, gravel and boulder; samples taken from below the surface were aerobic. Up to five centimetres of silt was recorded from the middle of the channel.
No aquatic plants were growing in the channel or on the water’s edge, and the only vegetation present were introduced terrestrial grasses and weeds.
The narrow riparian zone included large areas of bare ground and a sparsely vegetated cover provided by introduced grasses and weeds. The surrounding vegetation at the site was crop 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.|