South Para River, south-eastern edge of Gawler
2016 Aquatic Ecosystem Condition Report
Dry in autumn and slow-flowing channel in spring 2016
Sparse macroinvertebrate community with no rare or sensitive species present
Water was moderately fresh, clear, and showing obvious signs of nutrient enrichment
Riparian vegetation consisted of gums with grasses and native sedges.
About the location
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 river was given a Poor rating because the site sampled showed evidence of significant changes in ecosystem structure and function. There was evidence of human disturbance due to the extent of nutrient enrichment and disturbance of the riparian zone.
A sparse community of at least 24 species of macroinvertebrates was collected from the 6 m wide and up to 45 cm deep river in 2016. The river was dry in autumn but was a slow-flowing channel when sampled in spring. The community was dominated by large numbers of snails, limpets, amphipods, black fly larvae and leptocerid caddisflies, and smaller numbers of beetles, chironomids, waterbugs, damselflies and dragonflies, mayflies and caddisflies. A small amount of riffle was present at the site in spring and provided flowing habitat for blackfly larvae, baetid mayflies, and adults and larvae of the beetle Platynectes. All were tolerant and generalist species that are commonly found from pool habitats elsewhere in the region. The site lacked any rare or sensitive species, however two flow-dependent species, the beetle Platynectes and the blackfly Simulium ornatipes, were collected from the site in spring.
The water was moderately fresh (salinity 1,064 mg/L), well oxygenated (77% saturation), clear, and with moderately high concentrations of nutrients such as phosphorus (0.04 mg/L) and nitrogen (0.81 mg/L). Small patches of oils were also noticed on the edge of the creek in spring.
The sediments were dominated by detritus with some boulders, cobbles and sand also present. Samples taken from below the surface were black clays and silts that released sulphide when tested in spring, indicating that the sediments were occasionally anaerobic and lacking in oxygen. There were no signs of any significant areas of bank erosion at the site and the only animal droppings seen near the creek were from dogs.
A small amount of phytoplankton occurred at the site when the stream was wet (chlorophyll a 1.4 μg/L) and over 65% of the river was covered by aquatic plants, including reeds (Phragmites), cumbungi (Typha), sedges (Bolboschoenus and Cyperus) and dock (Rumex). The riparian zone was dominated by gum trees with grasses and native sedges and the surrounding vegetation beyond comprised urban gardens.
Special environmental features
The South Para River at Gawler provides no significant environmental values other than providing a connection from the upper catchment to its discharge point at the junction with the North Para River a few kilometres further downstream.
Pressures and 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.
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.