South Para River, Gawler
2013 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2013
- Likely to be nutrient enriched when wet due to the combined effects from local urban stormwater and upstream agricultural runoff
- Riparian vegetation consisted River Red Gums over introduced grasses, weeds and 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 at Gawler. The major land uses in the 33,640 hectare catchment are cereal cropping and stock grazing, with smaller areas used for plantation forestry, other minimal uses, residential, nature conservation, water storages and dams, irrigated horticulture, mining and roads. The monitoring site was located opposite the tennis courts off Lawrence Avenue within the township of Gawler.
The river was given a Poor rating because the site sampled showed evidence of relatively minor/significant changes in ecosystem structure and function. There was evidence of human disturbance due nutrient enrichment, weeds in the riparian zone, and the extent of urban housing and associated stormwater discharges throughout the lower reach of the South Para River.
The 8 m wide channel was dry in both autumn and spring 2013. No macroinvertebrate or water quality data was consequently available for this site.
The sediments were dominated by detritus and clay, with smaller amounts of boulder, cobble, gravel and sand also present; samples taken from below the surface were grey silts and showed no evidence that they had recently been anaerobic or lacking in oxygen. There were some signs of minor bank erosion affecting about 10 m of the site, which appeared to have been caused by people using the edge of the river as a recreational walking track.
Less than 10% of the channel was covered by a few species of aquatic plants, including sedges (Bolboschoenus and Cyperus) and reeds (Phragmites). Large mats of dried filamentous algae covered the channel in autumn, indicating that the river had been enriched with nutrients when it dried earlier in 2013. The riparian zone was dominated by scattered River Red Gums over introduced grasses, castor oil plants and a few native sedges and rushes. The surrounding vegetation near the creek comprised urban gardens.
Special environmental features
The South Para River at Gawler provides no significant environmental values, other than providing a connection from its upper catchment to the 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 (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.|
|Nutrient inputs to the creek from numerous diffuse sources (leading to extensive growth of algae and aquatic weeds)||The Adelaide and Mount Lofty Ranges NRM Board’s 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.