Pedler Creek, u/s Palm Valley
2016 Aquatic Ecosystem Condition Report
Ephemeral creek that was dry in autumn and spring 2016
Narrow channel dominated by fine sediments and gravel
Some bank erosion caused by past flood damage
Riparian vegetation comprising a few gums and wattles over a weedy understorey
About the location
Pedler Creek rises as several small, westerly flowing tributaries off the steep slopes of Sellicks Hill Range, south of Adelaide. They merge to form the main creek near Landcross Farm and it eventually discharges into Gulf St Vincent between Moana and Seaford. The major land uses in the 8,711 hectare catchment are vineyards (48%) and livestock grazing (26%), with smaller areas used for townships such as McLaren Vale and McLaren Flat, nature conservation, cropping and dams. The site selected for monitoring was located adjacent to vineyards off Main Road, between Landcross Farm and McLaren Vale.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and function. There was evidence of human disturbance due to the dominance of weeds in the limited riparian zone, and the extent of agriculture and urban land-uses in the catchment. The ephemeral nature of the creek would also limit the ability for this stream to provide significant in-stream habitats to support a rich aquatic life when it does hold water.
The 1.8 m wide channel was dry in both autumn and spring 2016. No macroinvertebrate or water quality data was consequently available for this site.
The sediments were dominated by sand and detritus, and included smaller amounts of silt, gravel, pebbles and clay. Samples taken from below the surface were grey sands and silt and showed no evidence that the sediments had recently been anaerobic or lacking in oxygen. Only a small amount of bank erosion extending over about 10% of the site was noted, which had presumably been caused by past flood damage.
Patches of a sedge (Bolboschoenus) extended over more than 10% of the channel and the presence of dried algal mats in spring indicate that the creek was wet for some weeks to months during winter. The riparian zone comprised a few gums and wattles over sedges (Isolepis and Carex) and weed species that included olive trees, wild roses and various introduced grasses. The surrounding vegetation near the creek comprised vineyards and a recreational park with its associated plantings.
Special environmental features
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.