Blackford Drain is a large drain in the lower South East with a catchment area of over 500 km2. It rises at an elevation about 25 metres above sea level a few kilometres west of Lucindale and drains in a northerly direction, receives water from the Jacky Winter Drain, and eventually discharges into the Southern Ocean at Lacepede Bay, four kilometres north of Kingston SE.
Blackford 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 major land uses are agricultural cropping and grazing with small areas of remnant native vegetation. The monitoring site was located in the lower reaches near the gauge station off Williams Road, about four kilometres north of Kingston SE.
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 nutrient enrichment, salinisation and poor riparian habitat, although the drain still provided a refuge for many salt tolerant native species.
Findings
A moderately diverse community of about 33 species of macroinvertebrates was collected from this drain in 2009. The habitats ranged from a shallow (12 cm deep) series of isolated pools in autumn to a flowing channel up to 35 metres wide and over one metre deep in places in spring. The community was dominated by species tolerant to salinity and poor water quality and included low numbers of amphipods and waterbugs in autumn and higher numbers of amphipods, chironomids and corixid waterbugs in spring. The only rare species detected was a single freshwater crayfish or land yabby from the genus Geocharax, collected in spring.
The water was saline (salinity ranged from 7,438-8,461 mg/L), well oxygenated (109-114% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (1.07-1.17 mg/L) and phosphorus (0.03-0.05 mg/L).
The sediments were dominated by detritus, algae, silt and small amounts of cobble and gravel; samples taken from below the surface were blackened, sulfidic and anaerobic, or lacking in oxygen.
Large growths of aquatic plants grew in the channel and on the water’s edge and included submerged (Ruppia and Nitella) and emergent species (Cotula, Juncus and Mimulus). There was also a large amount of filamentous algae present within the channel, particularly in spring when over 35% of the channel was covered in sheets of green algae.
The narrow riparian zone was comprised weeds and grasses, with no trees or large shrubs present. The surrounding vegetation at the site was largely native woodland consisting of eucalypts, wattles and paperbarks over grasses and weeds.
Special environmental features
The lower reach of Blackford Drain provides habitat for a rare and regionally endemic freshwater crayfish (Geocharax). It also supports hardyhead fish and a large number of salt tolerant macroinvertebrate species.
Pressures and management responses
Pressures
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.
Observed Condition
Expected Condition
