Yettie Creek, near Williamstown
2008 Aquatic Ecosystem Condition Report
- Affected by nutrient enrichment and fine sediments.
- Macroinvertebrate community dominated by species tolerant of pollution.
- Weedy riparian vegetation and excessive aquatic plant growths.
- Despite the impact of human activity provides habitat to two rare species.
About the location
Yettie Creek rises west of Williamstown in the Mount Lofty Ranges and flows through mainly livestock grazing areas into the Barossa Reservoir. The narrow stream eventually becomes Cockatoo Creek and discharges into the South Para River, about five kilometres southeast of Gawler.
The site selected for sampling was downstream from the Whispering Wall, off Whispering Wall Road, northwest of Williamstown.
The creek was given a Fair rating at this site because the ecosystem showed moderate changes to animal and plant life, and some changes to the way the ecosystem functions. The site was affected by land uses in the catchment that have released high levels of fine sediments and nutrients into the stream.
At the time of sampling in Spring 2008, the creek consisted of narrow, one-metre wide, isolated pools.
A diverse community of 48 species of macroinvertebrates was collected from the shallow pool habitats. The community was dominated by species tolerant to high nutrient levels, and included large numbers of juvenile snails, worms and mites. Small numbers of species sensitive to pollution were also found, including a stonefly and a chironomid.
The water was moderately fresh (salinity of 1,500 mg/L) and moderately well oxygenated (59% saturation). It was slightly cloudy or turbid, and slightly coloured, with moderate levels of nutrients such as nitrogen (0.54 mg/L) and phosphorus (0.03 mg/L).
Dense areas of the reed-like aquatic plant Cumbungi (Typha domingensis) shaded the water and limited the potential for significant algal growth. Sucker regrowth from willow and ash trees, and other introduced grasses and understorey plants dominated the banks, or riparian zone, with occasional River Red Gums the only obvious native plants. Vegetation in the surrounding landscape was mainly eucalypt woodland with small clumps of individual cherry trees.
Special environmental features
The creek provides habitat for at least two rare and sensitive species–a stonefly (Austrocerca tasmanica) and one chironomid (Orthoclad wood miner species 1).
Pressures and management responses
|Extensive deciduous tree 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.|
|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.|
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.