Yadnapunda Creek, Matthewson Spring
2012 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2012
- Likely to be enriched with nutrients when wet because the catchment is grazed by stock
- Some bank erosion caused by stock and native animals accessing the creekbed
- Riparian vegetation consisted of native trees and shrubs
About the location
Yadnapunda Creek is a medium-sized intermittent stream that rises east from Wilpena Pound in the Southern Flinders Ranges and flows in an easterly direction before eventually discharging into Wilpena Creek to the south of Martins Well. Wilpena Creek flows into the Siccus River and then drains onto the plains on the southern edge of Lake Frome; flow only extends through the creek system and onto the plains during exceptionally wet years. The dominant land use in the 10,398 hectare catchment, upstream from the site sampled, is grazing natural vegetation. The monitoring site was located off an unsealed road to Hawker, about 35 km east from Wilpena.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance including stock accessing the banks and causing some erosion but the stream provides physical habitat complexity and supports a range of native aquatic and riparian plants.
The 2 m wide spring occurs within a broad 200 m wide channel, and both habitats were dry in autumn and spring 2012. No macroinvertebrate or water quality data was consequently available for this site.
The sediments were dominated by detritus, clay and sand, with smaller amounts of gravel and silt also present. Samples taken from below the surface were sands and showed no signs that the sediments were recently anaerobic, or lacking in oxygen. About 10 m of bank showed evidence of erosion caused by cattle and possibly kangaroos accessing the creekbed.
Several types of aquatic plants (Cyperus gymnocaulos, Juncus and Typha) were recorded from the dry channel but there was no evidence of any algal remnants among the damp sediments at the site. The riparian vegetation was dominated by acacias and paperbarks over wattles, chenopods and grasses on the moderately well vegetated banks (50-79% vegetative cover). The surrounding vegetation at the site comprised low native shrubland dominated by wattles, bluebush and samphire.
Special environmental features
Yadnapunda Creek is a largely natural, ephemeral stream from the low rainfall part of the Flinders Ranges, east from Wilpena Pound. Stock grazing is the dominant land use but limited road access to the catchment prevents many of the other types of disturbances that are normally associated with human settlement. No significant environmental values were recorded from the dry site in 2012. However, a range of insects and mites were recorded from the same location in 1998, so the creek can support a generalist and tolerant aquatic fauna when it holds water.
Pressures and management responses
|Livestock have direct access at the site and upstream exerting excessive grazing pressure on vegetation, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds
|The SA Arid Lands Natural Resources Management Board recognizes that both direct and diffuse impacts on aquatic ecosystem condition can occur through direct stock access and excessive grazing pressure from stock and feral herbivores. Technical advice and incentives are offered to land managers in the region, as funding permits, to address these impacts through appropriate activities suitable for the context. In addition, projects are underway across the region to identify, prioritise and address impacts at key aquatic sites.