Tributary of Yankalilla River, SE from Torrensvale
2013 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2013
- Likely to be enriched with nutrients due to the surrounding land uses in the catchment
- Riparian vegetation lacked any trees or shrubs and only comprised introduced grasses
- Bank erosion was extensive and appeared to have been caused by cattle accessing and damaging the bed and banks of the creek
About the location
Tributary of Yankalilla River is a very small first order stream in the Southern Mount Lofty Ranges that rises at an elevation of about 145 m, and flows north for a few hundred metres, before joining other creeks to form the Yankalilla River. This river then continues flowing in a north-westerly direction, where it eventually discharges into Gulf St Vincent at Yankalilla Bay. The major land uses in the 4.7 hectare catchment were irrigated pastures (54%), other minimal uses (26%), dairy grazing of modified pastures (12.6%) and rural residential living (7%). The site sampled was located within a dairy paddock and was accessed via a track off Willow Creek Road, 1 km north-east from ‘Rockwella’ and about 2.5 km south-east from Torrens Vale.
The creek was given a Very Poor rating because the site sampled showed evidence of major changes to both the animal and plant life inhabiting the stream, and a significant breakdown in the way the ecosystem functions. There was evidence of significant human disturbance due to the extent of bank erosion, cattle droppings and weedy grasses in the riparian zone.
The 3-4 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, with smaller amounts of sand, clay and silt also present; samples taken from below the surface were grey silts and clays that showed no evidence to indicate that the sediments had recently been anaerobic or lacking in oxygen. There was a heavy amount of bank erosion recorded at the site, with over 50% of the banks showing signs of damage caused by cattle regularly accessing the stream. The only animal droppings seen in the creek and on the banks were from cattle.
Some dried deposits of a type of filamentous alga (Cladophora) and a small aquatic plant called a starwort (Callitriche), each covered nearly 10% of the channel in autumn, which indicates that the creek had been enriched with nutrients prior to its recent drying. No signs of any algae or aquatic plants were seen during the spring survey, and the presence of terrestrial grasses in the channel indicates that the creek had largely remained dry during the wetter months of the year. The riparian zone lacked any trees or shrubs and only comprised introduced grasses. The surrounding vegetation near the creek comprised only a few scattered gum trees over pasture used to graze dairy cattle.
Special environmental features
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.|
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.