Riparian vegetation consisted of native species and introduced grasses
Area map
About the location
Ballaparudda Creek rises about 3 kilometres south-east from Parawa on the Fleurieu Peninsula at an elevation of about 300 m, and flows in a southerly direction for several kilometres before discharging into the Southern Ocean at Ballaparudda Beach. The major land uses in the 871 hectare catchment upstream from the site are grazing pastures (47%), hardwood plantation forestry (29%), sown grasses (15%) and native vegetation (7%), and smaller areas used for roads, dams and rural residential living. The monitoring site was located in the lower reaches of the stream just north from Mount Scrub Road.
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 filamentous algae and elevated nitrogen concentrations. The stream provides habitat for a range of rare, sensitive and flow-dependent species of macroinvertebrates.
Findings
A diverse community of at least 44 species of macroinvertebrates was collected from the creek (26 species in autumn and 29 in spring), 2-2.8 m wide and up to 42 cm deep, in autumn and spring 2016. The creek consisted of mostly slow-flowing to still pools (60-70%) connected by fast-flowing riffle habitats (30-40%), with slightly more riffle habitat present in spring than in autumn. The community was dominated by amphipods, chironomids and stoneflies, with smaller numbers of snails, mites, yabbies, springtails, beetles, craneflies, mosquitoes, biting midges, blackflies, mayflies, waterbugs, dragonflies and caddisflies. A number of rare, sensitive and or flow-dependent species were collected from the site, including blackflies (Austrosimulium and Simulium), a chironomid (Rheotanytarsus), mayflies (Offadens, Atalophlebia australasica, Atalophlebia australis, Nousia fuscula and Thraulophlebia inconspicua), a dragonfly (Synthemis eustalacta), stoneflies (Illiesoperla mayii and Dinotoperla evansi) and caddisflies (Taschorema evansi and Cheumatopsyche).
The water was fresh (salinity ranged from 312-595 mg/L), well oxygenated (75-84% saturation), clear but slightly coloured, and with generally moderate to high concentrations of nutrients such as phosphorus (0.04-0.06 mg/L) and nitrogen (0.78-1.44 mg/L).
The sediments were dominated by detritus, bedrock, sand and silt in the pools and by detritus, boulder ad cobble in the riffles; samples taken from below the surface were mostly grey clay and silt that did not release any sulfide when tested, indicating that the sediments were well aerated. There was no evidence of any significant bank erosion but sheep droppings were seen in the vicinity of the creek in autumn.
Only a small amount of phytoplankton was recorded in the creek (chlorophyll a ranged from 1.03-1.23 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 sedges (Cyperus and Isolepis), pennywort (Hydrocotyle), water ribbons (Triglochin), dock (Rumex), and knotweed (Persicaria). The narrow riparian zone comprised mostly sedges, rushes and introduced grasses with a few scattered gum trees lining the banks. The surrounding terrestrial vegetation was cleared grazing land with isolated gums in the local landscape, and a blue gum forest was located downstream from the site sampled.
Special environmental features
The creek supported a wide range of significant aquatic macroinvertebrates, including a dragonfly and several blackflies, mayflies, stoneflies and caddisflies. The presence of such a significant area of flowing riffle habitat is also notable due to the importance of habitat diversity in sustaining the biodiversity of streams in the region.
Pressures and management responses
Pressures
Management responses
Nutrient inputs to the creek from numerous diffuse sources (potentially leading to excess growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board land management program encourages and promotes managing land to improve water quality. This includes working with industry and landholders to ensure efficient use of fertilisers and discuss ways to reduce runoff of nutrients into waterways.
Insufficient natural water flows in the creek resulting from water extraction and climate variability
Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.
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.
Observed Condition
Expected Condition
