Driver River, near Verran
2015 Aquatic Ecosystem Condition Report
Permanently wet, saline, slow-flowing stream in autumn and spring
Depauperate macroinvertebrate community with no rare or sensitive species
Obvious signs of gross nutrient enrichment
Riparian vegetation limited to samphire, paperbark and bare soil
Large silt deposit in the channel
About the location
Driver River is a small stream in Eyre Peninsula that rises between Verran and Rudall, and flows in a south-easterly direction before discharging into an intermittent coastal swamp about 12 kilometres south-west from Arno Bay. The major land uses are grazing and cropping. The monitoring site was located off the Balumbah-Kinnard Road, about four kilometres north from Verran.
The river was given a very poor rating because the site sampled showed evidence of major changes in ecosystem structure and a significant breakdown to the way the ecosystem functions. There was considerable evidence of human disturbance, including salinization, nutrient enrichment, fine sediment deposition and poor riparian habitat. High salinity and acidic water clearly contribute to the degraded condition of this stream, which lacks plants, despite the presence of nutrients in the water, and only supports a few highly tolerant and mobile macroinvertebrates.
A very sparse community of about 6 species of macroinvertebrates (2 in autumn and 5 in spring) was collected from the slow-flowing stream, 1.2-2.5 metres wide and up to 15 centimetres deep in autumn and spring 2015; water levels were more extensive than normal in autumn due to heavy rainfall that occurred in the area prior to sampling. The community comprised salt-tolerant isopod crustaceans (Haloniscus), three dytiscid beetles (Necterosoma penicillatus, Laccobius and bidessinae larvae), biting midges (Culicoides), and a chironomid (Paralimnophyes).
The water was saline (salinity of 16,582 mg/L in autumn and 39,985 mg/L in spring), well oxygenated (82-100% saturation), acidic (pH 3.58-4.57), slightly turbid, and with very high concentrations of nutrients such as nitrogen (1.98-2.95 mg/L) and phosphorus (0.09-0.13 mg/L).
The sediments were dominated by clay, sand and detritus, with smaller amounts of gravel, silt, bedrock and cobble also present. Samples taken from below the surface were grey sands that had an anaerobic odour and released sulfide when tested in autumn, indicating that the sediments occasionally lacked oxygen and were a harsh environment for benthic species to be able to tolerate. A deposit of 5-10 centimetres of silt covered the streambed in places but there was no evidence of any significant areas of bank erosion near the site sampled. The only animal droppings seen near the stream were from kangaroos.
A low to moderate amount of phytoplankton (chlorophyll a ranged from 0.88-7.5 µg/L) was recorded but there were no signs of any filamentous algal growths noted during either survey. About 10% of the edges of the stream were covered by samphire but no aquatic plants were recorded in the river. The riparian zone consisted of salt-tolerant paperbark trees (Melaleuca) over samphire and bare soil. The surrounding vegetation was cereal cropping land with a few scattered mallee gums present in the general landscape.
Special environmental features
Pressures and management responses
Livestock have direct access at the site and upstream in the catchment, causing sediment erosion and adding excessive nutrients.
The Eyre Peninsula NRM Board administer the Water Affecting Activities permits and polices for the region. This process allows the Board to grant or refuse permits to undertake certain activities affecting water resources. The process is the region’s primary means of preventing any potential impact on the environmental integrity of surface water catchments.
The Eyre Peninsula NRM Board continues to promote managing land to improve water quality. This includes incentives for:
The Eyre Peninsula NRM Board also undertakes a native freshwater fish monitoring program throughout this catchment.
Limited natural riparian vegetation at the site and upstream in the catchment, providing minimal buffer protection from catchment land uses.