Pekina Creek, Pekina
2012 Aquatic Ecosystem Condition Report
- Dry in autumn and spring 2012
- Likely to be enriched with nutrients when wet due to the extent of agricultural development in the catchment
- Some bank erosion caused by past flood damage and evidence of stock accessing the creekbed
- Riparian vegetation consisted of a sparse gum tree cover over introduced grasses and weeds
About the location
Pekina Creek rises south from Pekina off the eastern side of Pekina Ranges in the Southern Flinders Ranges, and flows in a north-north-easterly direction for about 16 km into Pekina Reservoir; downstream from the reservoir the creek eventually disappears underground on the Walloway Plain, north-east from Orroroo. The major land uses in the 4,327 hectare catchment, upstream from the site, are cereal cropping and grazing modified pastures; only 1% of the catchment retains a cover of remnant native vegetation. The monitoring site was located to the north of Pekina off the Melrose Road, about 12 km south-west from Orroroo.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure, and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance including stock access, fine sediment deposition and degraded weedy riparian habitats.
The sediments were dominated by detritus, with smaller amounts of sand and clay also present. Samples taken from below the surface were red sands and clays, 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 past flood damage. Sheep faeces were noted throughout the creekbed and banks of the site inspected.
Only one type of aquatic plant was recorded (sedge Cyperus gymnocaulos) and there was no evidence of any algal remnants among the dry sediments in the channel. The riparian vegetation was dominated by introduced grasses and weeds, with a few scattered River Red Gums and sedges on the moderately well vegetated banks (50-79% vegetative cover). The surrounding vegetation at the site comprised cropping and grazing land with only a few scattered gum trees in the local landscape.
Special environmental values
Pekina Creek is an ephemeral stream that lies within an agricultural landscape in the Mid North of the State. No significant environmental values were recorded from the dry site in 2012. Previous sampling of the same site in 1997 recorded a saline tolerant, generalist sort of aquatic community with no sensitive, rare or regionally significant species. The salinity ranged from 2,500-3,300 mg/L which exceeds the salinity tolerance of most freshwater aquatic macroinvertebrates and plants, so the catchment is unlikely to support a wide range of species when surface water flows in the creek.
Pressures and management responses
|Livestock have direct access at the site and upstream in the catchment exerting excessive grazing pressure on vegetation, causing sediment erosion and adding excessive nutrients to the watercourse.||
The Northern and Yorke Regional NRM Plan has the following Resource Condition Targets:
Natural Resources (Northern and Yorke) has also been updating its understanding and management of the Willochra Catchment:
|Broad acre cropping in the catchment, adding excessive nutrients to the watercourse.|