Saunders Creek, near Sanderston
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and consisting of saline, isolated pools in spring
- Sparse macroinvertebrate community with no rare or sensitive species
- Obvious signs of moderate nutrient enrichment
- Riparian vegetation consisted of gums over introduced grasses and weeds
About the location
Saunders Creek is a moderately large stream in the eastern Mount Lofty Ranges. It rises east of Springton and flows in an easterly direction before discharging into the River Murray, north-east of Mannum. The major land uses are sheep grazing, cropping and recreational use of the Gorge Sanctuary.
The monitoring site was located on a track south of the Glen Roy Stud property at the northern end of Milendella Road, over one kilometre north-west of Sanderston.
The creek was given a Fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance, including a lack of remnant vegetation, nutrient enrichment and poor riparian habitat.
A sparse community of about 19 species of macroinvertebrates was collected from isolated pool habitats, up to four metres wide and eight centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by species tolerant to high salinity and poor water quality such as corixid waterbugs (Agraptocorixa), amphipods (Austrochiltonia australis) and leptocerid caddisflies. It also included smaller numbers of mites, beetles, mosquitoes, chironomids (Procladius, Chironomus and Dicrotendipes), baetid mayflies (Cloeon), waterbugs (Microvelia and Anisops), damselflies and caddisflies (Oecetis and Triplectides). No sensitive or rare species were found, although many tadpoles were recorded in the shallow pool in spring.
The water was saline (salinity of 3,327 mg/L), well oxygenated (105% saturation) and slightly coloured, with moderate to high concentrations of nutrients such as nitrogen (1.13 mg/L) and phosphorus (0.04 mg/L).
The sediments were dominated by detritus, cobbles, sand and clay; samples taken from below the surface showed no signs that the sediment was lacking in oxygen.
Filamentous algae was not observed in the channel in 2010 but more than 10% of the creek was covered in sedges (Cyperus) and rushes (Juncus).
The riparian zone consisted of introduced grasses, weeds (e.g. soursobs and fennel) and sedges, under a few River Red Gums. The surrounding vegetation consisted native trees and shrubs such as gums, acacias and sheoaks over introduced grasses and weeds (e.g. Salvation Jane).
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 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.|
|Widespread introduced trees and weeds in the riparian zone at the site and upstream in the catchment (reducing habitat quality).||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.|
|Saline groundwater inflow (reducing ecological integrity).||Saline groundwater inflows may be exacerbated by two things; vegetation clearing and resultant increase in rainfall recharge, or the extraction of surface water reducing the dilution factor in natural saline discharge zones. The SA Murray–Darling Basin NRM Board’s Land Management Program strategically invests in salinity ‘hotspots’ by providing incentives to land managers to plant perennial pasture/fodder crops/ or revegetation to reduce recharge. The NRM Board works with various agencies to minimise any further vegetation clearing which may impact on the catchment’s water balance. The NRM Board seeks to manage and provide for environmental flows to allow natural dilution of saline waters through the development of Water Allocation Plans and Water Affecting Activity policies across the region.|