South Para River, south from Gawler
2011 Aquatic Ecosystem Condition Report
- Permanently wet, flowing, freshwater stream in autumn and spring 2011
- Diverse macroinvertebrate community with many rare, sensitive and flow-dependent species
- Obvious signs of moderate nutrient enrichment
- Riparian vegetation dominated by gums, sedges and weeds.
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 on a track off Gawler-One Tree Hill Road, about 3 km ESE from Bibaringa. The major land uses in the 28,229 hectare catchment are stock grazing, forestry and remnant native vegetation, with smaller areas used for conservation, water storages, quarries, various agricultural activities and residential living.
The river 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 including nutrient enrichment and degraded riparian vegetation but the stream provides habitat for several rare and sensitive species of macroinvertebrates.
A diverse community of at least 56 species of macroinvertebrates was collected from the flowing river, 5.5-13.1 m wide and over 1 m deep in places, in autumn and spring 2011. The river consisted of still to slow-flowing pools connected by fast-flowing riffle habitats; flow releases from the upstream reservoir contributed to the presence of the flowing habitats that were sampled. The community was dominated by generalists and species tolerant to poor water quality such as mites, corixid waterbugs, chironomids, blackflies and caenid mayflies (Tasmanocoenis). It also included smaller numbers of hydrozoans, limpets, native and introduced snails, worms, amphipods, freshwater shrimp, yabbies, springtails, beetles, craneflies, dixids, biting midges, mayflies, waterbugs and caddisflies. Several rare and sensitive species were collected, including a blackfly (Austrosimulium furiosum), chironomid (Podonomopsis), mayflies (Offadens, Atalophlebia australis and Thraulophlebia inconspicua) and caddisflies (Apsilochorema gisbum, Taschorema evansi and Ulmerochorema membrum). The site also provided habitat for several species normally associated with flowing water, including a blackfly (Simulium ornatipes), beetle (Platynectes decempunctatus), chironomid (Rheotanytarsus), caddisfly (Cheumatopsyche sp. 2) and most of the above-listed rare and sensitive species. The only fish seen at the site was an introduced pest called Mosquitofish (Gambusia).
The water was fresh (salinity ranged from 316-640 mg/L), well oxygenated (58-97% saturated), strongly coloured and slightly turbid, and with moderate to high concentrations of nutrients such as nitrogen (0.52-0.88 mg/L) and phosphorus (0.03 mg/L).
The sediments were dominated by detritus, cobble and silt in the slower-flowing sections and boulder, cobble and gravel in the riffles. Samples taken from below the surface were slightly blackened in colour and sulfidic, indicating that the sediments were anaerobic or lacked oxygen. Over 1 cm of fine silt covered the streambed in places but no evidence of any significant areas of bank erosion was noted at the site in 2011.
Small growths of filamentous algae (mostly Cladophora) were seen in spring and over 10% of the channel was covered by a few types of emergent plants (Cyperus, Juncus and Typha). The riparian vegetation consisted of River Red Gums over sedges, olives and other weeds and introduced grasses. The surrounding vegetation comprised scattered gum trees over olives and introduced grasses.
Special environmental features
The lower reaches of the South Para River supports a diverse range of aquatic species that include many rare, sensitive and flow-dependent macroinvertebrates.
Pressures and management responses
|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.|
|Livestock having direct access at the site and upstream (causing sediment erosion and adding excessive nutrients).||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 waterway and wetland fencing to exclude or limit stock from entering riparian zones.|
|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.|
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.