Riparian vegetation consisted of native wattles and gums over introduced grasses and weeds
Area map
About the location
First Creek is a small stream in the Southern Mount Lofty Ranges that rises on the western side of Mount Lofty and Crafers, and flows in a north-westerly direction where is becomes channelised through the north-eastern suburbs until it discharges into Torrens Lake near the Adelaide Zoo. The monitoring site was located upstream from the waterfall at Waterfall Gully. The major land use in the 515 hectare catchment upstream from the site is nature conservation (89%), due to the protection provided by Cleland Conservation Park, with small areas also used for residential living, roads and stock grazing.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance due to the extent of weeds in the riparian zone but the stream provides habitat for a significant number of rare, sensitive and flow-dependent species.
Findings
A diverse community of at least 39 species of macroinvertebrates was collected from the creek (29 species in autumn and 17 in spring), 3.2 m wide and up to 33 cm deep, in autumn and spring 2016. The creek consisted of mostly moderately fast-flowing, shallow riffle habitats with smaller areas of slow-flowing or still, shallow pool habitats in both sampling seasons. The community was not dominated by any particular species but consisted of a range of species present in low to moderate numbers, including the introduced snail Potamopyrgus, mites, beetles, biting midges, blackflies (including Austrosimulium furiosum and Paracnephia), chironomids (including the flow-dependent Rheotanytarsus), mayflies, dragonflies (including Austrogomphus and Hemigomphus), stoneflies (Dinotoperla evansi and Newmanoperla thoreyi) and caddisflies (including Tasimia, Ulmerochorema membrum, Lingora aurata, Atriplectides dubius and Notalina fulva). Most of the above-listed species were rare, sensitive and/or flow-dependent species. Juvenile galaxiid fish were also collected in spring.
The water was fresh (salinity ranged from 90-172 mg/L), well oxygenated (91-100% saturation) and clear, and with low to moderate nutrient concentrations such as phosphorus (0.01-0.02 mg/L) and nitrogen (0.35-0.64 mg/L).
The sediments were dominated by detritus, sand, cobbles and boulders with smaller amounts of pebble, gravel, silt, and filamentous algae in spring also present. Samples taken from below the surface were grey sands and there was no evidence to indicate that the sediments had recently been anaerobic or lacking in oxygen. Only small amounts of bank erosion were noticed in spring, likely due to recent higher flows through the site in winter.
There were only small growths of phytoplankton recorded (chlorophyll a ranged from <0.1-0.88 μg/L) but a filamentous alga (Spirogyra) covered a small portion of the site (<10%). Up to 35% area was covered by a few types of aquatic plants in autumn, including Crassula, Persicaria, Phragmites and Typha, although no aquatic plants were recorded in spring, possibly due to the large flows that went through the site during late winter. The narrow riparian zone consisted of a line of wattles and a few gum trees along each bank over introduced grasses and weeds and bracken. The surrounding vegetation beyond comprised dense native woodland within Cleland Conservation Park.
Special environmental features
First Creek provides a permanently flowing, freshwater stream that consistently supports a wide range of rare, sensitive and flow-dependent species. It is a major refuge for many species of blackflies, mayflies, stoneflies, caddisflies, and galaxiid fish. This creek probably represents the most natural stream in the Mount Lofty Ranges because only about 10% of the upstream catchment has been developed, and the remainder lies in a conservation park. This contrasts with other similar, least disturbed streams in the region where typically only 30-60% of the native vegetation remains following European settlement.
Pressures and management responses
Pressures
Management responses
Widespread introduced weeds in the riparian zone at the site and upstream
The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.
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.
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.
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
