The South Para River is a large stream in the Southern Mount Lofty Ranges that rises south from Mount Menge and flows in a general north-westerly direction, where it eventually joins with the North Para River to form the Gawler River in Gawler. The monitoring site was located off Gawler Terrace in Gawler South. The major land uses in the 30,885 hectare catchment are cereal cropping and stock grazing (37%), plantation forestry (18%) and other minimal uses (18%), with smaller areas of residential living, nature conservation, water storages, irrigated horticulture, mining and roads.
The creek was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure, and some changes to the way the ecosystem functions. There was evidence of human disturbance including nutrient enrichment.
Findings
The approximately 6 m wide channel was dry in autumn but contained very small isolated pools in spring 2015. Worms, the non-biting midges Procladius and Chironomus, snails, limpets, mites, beetles, mosquito larvae, a common mayfly, water boatmen, backswimmers, dragonflies, damselflies and a common species of caddisfly were found in the drying pools in spring.
The water was moderately fresh (salinity was 1,949 mg/L) with low oxygen levels (40% saturation) and was clear but slightly coloured. Small patches of oil were seen on the edges of the pools.
The sediments were dominated by cobbles, pebbles and detritus with some gravel and sand also present. No obvious signs of bank erosion were seen. More than 10% of the channel was covered in filamentous algae (dried algal mats and fresh strands of Spirogyra).
More than 35% of site was covered by a range of aquatic plants, including several emergent plants (Callitriche, Bolboschoenus, Cyperus, Rumex, Schoenoplectus and Typha). The 5 to 10 m riparian zone consisted river red gums with weedy grasses and nasturtians in understorey. The surrounding landscape was urban housing with exotic grasses and a recreational park.
Special environmental features
None detected. In the past, this ephemeral river has provided habitat for a more diverse community of macroinvertebrates include some flow-dependent species which were collected from riffle habitat present at this site.
Pressures and management responses
Pressures
Management responses
Insufficient natural water flows in the creek resulting from water extraction and climate variability (reducing ecological integrity).
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.
Widespread introduced weeds in the riparian zone at the site and upstream (reducing habitat quality).
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.
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.