Tributary of Oratunga Creek, First 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
- No evidence of any bank erosion but sheep accessed the banks of the stream during autumn
- Riparian vegetation consisted of native gums and shrubs over a largely native understorey
About the location
First Spring is a small, intermittent tributary of Oratunga Creek in the Northern Flinders Ranges that rises north from Breakneck Gorge and flows for about 6 km in a north-westerly direction before discharging into Oratunga Creek, about 500 m downstream from Oratunga. The only land use in the 4,500 hectare catchment, upstream from the site sampled, is grazing natural vegetation. The monitoring site was located off Glass Gorge Road, about 12 km north-west from Blinman
The creek was given a Very Good rating because the site sampled showed evidence of very little changes in ecosystem structure and function. There was evidence of minor human disturbance due to stock accessing the creekbed but the stream still provided a wide range of coarse sediment types and a near natural vegetation assemblage.
The sediments were dominated by bedrock, boulder and pebble, with smaller amounts of cobble, gravel, sand, silt and detritus also present. Samples taken from below the surface were grey silts and clay, and showed no signs that the sediments were recently anaerobic, or lacking in oxygen. No signs of any bank erosion was recorded but sheep had accessed and defaecated on the banks in autumn.
No aquatic plants or evidence of any dried algal deposits were recorded from the dry creekbed. The riparian vegetation was dominated by River Red Gums, White Cypress Pines, wattles and eremophilas over native grasses and understorey plants. The surrounding vegetation at the site comprised low woodland dominated by White Cypress Pines and acacias.
Special environmental features
First Spring is an ephemeral tributary of Oratunga Creek in a lightly grazed catchment that provided no significant environmental values when it was assessed as a dry site in 2012. Previous sampling of the same site in 1998, however, recorded a range of aquatic species from the pools that were present during a much wetter period. They included several regionally rare species (e.g. mites from families Oxidae, Limnesiidae and Pionidae, and caddisfly Orphninotrichia maculata) as well as a range of flow-dependent species (beetle Platynectes, biting midge Dasyhelea, blackflies and empidid flies) that commonly occur from flowing springs in the Flinders Ranges). So a rich aquatic fauna has been recorded from the site in the past when pool habitats persist for many months of the year.
Pressures and management responses
|Livestock and feral animals have direct access at the site and upstream, exerting excessive grazing pressure, causing sediment erosion and adding excessive nutrients to the watercourse.||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.|