Deep Creek, near Norton Summit
2016 Aquatic Ecosystem Condition Report
Permanently flowing stream in autumn and spring 2016
Diverse macroinvertebrate community with many rare, sensitive and flow-dependent species recorded
Water was fresh, clear and enriched with nutrients
Riparian vegetation consisted of woody weeds and understorey species
About the location
Deep Creek rises to the north of Summertown in the southern Mount Lofty Ranges, and flows northeast into Sixth Creek, about one kilometre east from Cherryville. The major land uses in the catchment upstream from the site include vineyards (33%), protected areas of native vegetation (31%) and livestock grazing (24%), with smaller areas used for horticulture, urban living and mining. The monitoring site was located off Knotts Hill Road, about four kilometres east of Norton Summit.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was minor evidence of human disturbance due to the presence of elevated nutrient concentrations and a weedy riparian zone but the stream provides habitat for a large number of rare, sensitive and flow-dependent species of macroinvertebrates.
A diverse community of at least 57 species of macroinvertebrates was collected from the creek (31 species in autumn and 45 in spring), 1.8-5 m wide and over 1 m deep, in autumn and spring 2016. The creek consisted of fast-flowing riffles connecting slow-flowing to still pools, with more riffles present in autumn (70%) and pools in spring (60%). The community was dominated by chironomids, with smaller numbers of flatworms, snails, worms, mites, amphipods, yabbies, springtails, beetles, dixids, mosquitoes, blackflies, biting midges, soldierflies, mayflies, waterbugs, damselflies, dragonflies, stoneflies and caddisflies. Most were generalist and tolerant macroinvertebrates but a number of rare, sensitive and/or flow-dependent species were also collected, including an elmid beetle (Simsonia), chironomid (Rheotanytarsus), blackflies (Austrosimulium and Simulium), mayflies (Atalophlebia australasica and Thraulophlebia), stoneflies (Dinotoperla and Austrocerca) and caddisflies (Taschorema evansi, Taschorema complex, Tasimia, Lingora, Atriplectides and Triplectides similis). The only fish recorded were some juvenile trout that were seen in the pools in spring .
The water was fresh (salinity ranged from 123-215 mg/L), well oxygenated (74-95% saturation), clear but slightly coloured, and with generally moderate to high concentrations of nutrients such as phosphorus (0.04-0.1 mg/L) and nitrogen (0.38-1.52 mg/L).
The sediments were dominated by detritus, silt and sand in the pools and by detritus, boulder and pebbles in the riffles; samples taken from below the surface were mostly grey clay and silt that released no sulfide when tested, indicating that the sediments were well oxygenated. There was moderate evidence of bank erosion seen in spring, which was attributed to recent winter flood damage. No stock or other animal droppings were seen in the vicinity of the creek.
Only a small amount of phytoplankton was recorded during the year (chlorophyll a ranged from 0.49-0.68 μg/L), and filamentous algae (Cladophora) was only seen in spring, when it extended over nearly 10% of the creek. A slightly larger area was also covered by aquatic plants, including knotweed (Persicaria), introduced watercress (Rorippa), dock (Rumex) and rushes (Juncus).The riparian zone was dominated by woody weeds such as willows and blackberries, with an understorey of introduced grasses and bracken. The surrounding vegetation comprised dense woodland on one bank and grazed open woodland on the other bank.
Special environmental features
The site provided significant riffle and pool habitats that supported a wide range of generalist, tolerant, rare and sensitive species of macroinvertebrates. The presence of the elmid beetle and caddisfly from the Family Tasimiidae were particularly notable records for the stream and region.
Pressures and management responses
Limited riparian zone vegetation at the creek and upstream (reducing habitat quality, increasing sediment erosion)
The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion. The Board also partner with local government to deliver a number of watercourse revegetation projects across the region.
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.