South Para River, south-eastern edge of Gawler
2008 Aquatic Ecosystem Condition Report
- Significantly affected by low flows, salinity and high nutrient levels.
- Sparse macroinvertebrate community dominated by species tolerant of pollution.
- Limited riparian zone invaded by weeds.
- Provides habitat for frog species.
About the location
South Para River rises in the Mount Crawford Forest about five kilometres northwest of Mount Pleasant in the southern Mount Lofty Ranges. Two in-stream reservoirs–South Para and Warren–capture water in the upper reaches, with the river ultimately flowing through Gawler’s southern residential area where it joins the North Para River to form the Gawler River. The main land uses in the catchment include pine and eucalypt forests, conservation and recreation parks, grazing and cereal cropping.
The site selected for monitoring was located in the lower reaches of the river, off Gawler Terrace, within the township area.
The river was given a Poor rating at this site because the ecosystem showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystem functions due to low flows, salinity effects and poor riparian habitat.
When the site was sampled in October 2008, the river formed a series of isolated pools which provided habitat to a sparse community of only 23 macroinvertebrate species. They were dominated by various chironomids, snails, worms and nematodes that are tolerant to poor water quality. No sensitive species were collected.
The water was saline (salinity of about 3,000 mg/L), well oxygenated (72% saturation), slightly coloured and cloudy, or turbid. It contained moderate to high concentrations of nutrient such as nitrogen (0.98 mg/L), phosphorus (0.07 mg/L) and organic carbon (13.2 mg/L).
Large growths of aquatic plants covered up to 35% of the channel. Patches of Common Reed (Phragmites australis) and sedge (Bolboschoenus caldwellii) grew around the water's edge, and stonewort (Chara) was found in the deeper water.
River Red Gum woodland grew over introduced grasses and herbs in the riparian zone. The shrub and understorey vegetation was dominated by exotic shrubs, woody weeds and introduced grasses such as ash and pepper trees, castor oil plants, kikuyu and paspalum grasses, spurges (Euphorbia) and nasturtiums.
Special environmental features
South Para River at this site provides a breeding habitat for large numbers of tadpoles from common frog species such as the Brown Froglet and Marsh Frog.
Pressures and management responses
|Extensive introduced trees and weed growth 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.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||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.|
|Large decrease in natural water flows (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.|
|Saline groundwater inflow (reducing ecological integrity)||The Adelaide and Mount Lofty Ranges NRM Board has installed telemetered groundwater monitoring stations at key locations within the region. These are monitored for level and salinity; unusual results (such as high salinity influxes) are investigated.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA and prepared in conjunction with the Adelaide and Mount Lofty Ranges NRM Board.