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Picks Swamp Outlet Drain, west from Piccaninnie Ponds Conservation Park
- Permanently wet with a slow-flowing channel present in autumn and spring 2009.
- Moderately diverse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation limited to introduced grasses and native sedges.
- Large silt deposits in the channel.
About the location
Picks Swamp Outlet Drain is a small coastal drain in the lower South East that collects water from a small catchment area around Picks Swamp. It discharges into the Southern Ocean at Discovery Bay, to the west of Piccaninnie Ponds. The major land uses are grazing and cropping, and large areas of remnant native vegetation also remain in the catchment.
Picks Swamp Outlet 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 off an access track from ACI Road near the estuarine part of the drain, about 16 kilometres east from Port MacDonnell.
The drain was given a Fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance, including nutrient enrichment, poor riparian habitat and fine sediment deposition.
A moderately diverse community of about 37 species of macroinvertebrates was collected from the slow-flowing channel, two to four metres wide and up to 30 centimetres deep, in autumn and spring 2009. The community was dominated by generalists and species tolerant to poor water quality such as introduced snails (Potamopyrgus), native snails (Glyptophysa), amphipod crustaceans (Austrochiltonia australis) and hypogastrurid springtails. No sensitive or rare species were found but the site supported several uncommonly collected species from the region, such as nemerteans or proboscis worms, a mollusc called a little basket shell (Corbiculina), and mites from the family Unionicolidae.
The water was fresh (salinity ranged from 509–605 mg/L), well oxygenated (91–139% saturation) and clear, with very low phosphorus concentrations (<0.005–0.006 mg/L) and high nitrogen concentrations (2.07–2.51 mg/L).
The sediments were dominated by detritus, sand, algae and silt; samples taken from below the surface were aerated and not obviously blackened and anaerobic. Large deposits of silt, 5–10 centimetres deep, were recorded from the middle of the drain.
Submerged (Chara) and emergent plants (Cotula, Isolepis, Juncus, Ranunculus, introduced Rorippa, Rumex and Typha) were growing in the channel and on the water’s edge. These plants were particularly abundant in spring when they covered more than 65% of the drain. The growth of filamentous algae was also moderately extensive in spring, when it covered over 10% of the channel.
The narrow riparian zone was limited to sedges (Isolepis) and introduced grasses. The surrounding vegetation at the site was mostly cleared grazing and cropping land, with small patches of native vegetation around the swamp habitats in the local area.
Special environmental features
Picks Swamp Outlet Drain provides habitat for a range of uncommonly collected macroinvertebrates from the region and at least one threatened species of fish called the Southern Pygmy Perch.
Pressures and management responses
|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.|