Preamimma Creek, near Callington
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment and fine sediment.
- Creekbanks extensively eroded by livestock and flood events.
- Severely disrupted riparian zone with no trees and dominated by weeds.
About the location
Preamimma Creek is a very small stream in the southern Mount Lofty Ranges, which rises 12 kilometres east of Dawesley. It flows only occasionally, through agricultural land used mainly for sheep grazing and cereal cropping, into the Mobilong Swamp on the River Murray floodplain.
The site selected for monitoring was located off Anders Road, near Rockleigh Downs, about nine kilometres north-east of Callington.
The creek was given a Poor rating at this site because the ecosystem showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystem functions. The habitat had been severely disturbed, and evidence indicated the channel would carry very high nutrient and salt loads when wet.
The creek channel was dry when the site was inspected in November 2008, and showed no evidence of being recently wet.
Information collected from the same location in spring 1999 when it was flowing, showed the water was saline (salinity of 5,200 mg/L) and the nitrogen concentration was low (0.48 mg/L) but the phosphorus concentration was high (0.17 mg/L). It was also alkaline, with an elevated pH reading (9.24) due to the presence of a large algal bloom.
When the creek was sampled in autumn 1999, it was also a much smaller creek and the salinity and nutrient concentrations were much higher (salinity of 15,000 mg/L, nitrogen 5 mg/L and phosphorus 0.25 mg/L).
In 2008, the channel was covered with oats (Avena) and small patches of Spiny Sedge (Cyperus gymnocaulos). Sheep and rabbits had grazed the area extensively, leaving behind considerable amounts of manure.
The sediments were mostly sand and silt; there was no evidence of dried algae or the sediments being blackened or anaerobic. Most of the creek’s banks were significantly eroded by livestock accessing the area, and occasional flood events.
There were no trees growing along the banks in the riparian zone, and only small numbers of introduced tobacco trees (Nicotiana) were present as an overstorey shrub layer. Introduced grasses and weeds dominated the local area, with small patches of native plants such as Sea Rush (Juncus kraussii) and Spiny Sedge in some places.
Special environmental features
Pressures and management responses
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||The SA Murray–Darling Basin NRM Board acknowledges the significant impacts that livestock have on aquatic environments and seeks to provide free technical advice and incentives to land managers for fencing and other works as funding permits. Funding incentives are limited in value and extent and require land managers to volunteer to be involved.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The SA Murray–Darling Basin NRM Board recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.|
|Extensive weed growth in the riparian zone at the site and upstream (causing habitat disturbance).||The SA Murray–Darling Basin NRM Board recognises the limitations of available funds relative to the scale of the degradation caused by introduced trees and weeds. The NRM Board provides free technical advice and community education to assist land managers in dealing with the integrated management of aquatic weeds. The NRM Board also has a targeted process, as directed by State Government, to strictly prioritise its investment in weed control activities as funds are limited. The NRM Board actively seeks funding opportunities for weed control; most opportunities are for locations where biodiversity outcomes can be achieved.|