Reedy Creek, near Caloote
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and saline, isolated pools present in spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation mostly consisted of reeds and River Red Gums.
About the location
Reedy Creek is a large stream in the eastern Mount Lofty Ranges that forms downstream from the junction of Baker and Harrison creeks to the south-east of Palmer, and flows in an easterly direction where it discharges into the River Murray, downstream of Mannum. The major land uses are stock grazing and cropping, with small areas of native vegetation remaining in parts of the catchment.
The monitoring site was located downstream from a waterfall within a recreation reserve on a track off Cascade Road, about five kilometres north-west of Caloote.
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 nutrient enrichment, bank erosion and fine sediment deposits in the stream.
A sparse community of about 17 species of macroinvertebrates was collected from isolated pools, up to 17 metres wide and 85 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by species tolerant to poor water quality and high salinity, such as chironomids (including Tanytarsus, Chironomus and Dicrotendipes) and amphipods (Austrochiltonia australis). It also included smaller numbers of mites, beetles, mosquitoes, waterbugs, damselflies and leptocerid caddisflies. No sensitive or rare species were found. The only fish collected was the introduced mosquitofish (Gambusia) and a few carp were also seen at the site in spring.
The water was saline (salinity of 5,801 mg/L), poorly oxygenated (30% saturation), clear but strongly coloured, with moderate to high concentrations of nutrients such as nitrogen (1.76 mg/L) and phosphorus (0.05 mg/L).
The sediments were dominated by detritus, gravel, sand and silt; samples taken from below the surface showed no indications that the sediment was lacking in oxygen. A small amount of silt was recorded from the channel in places and less than 10 metres of the bank showed signs of erosion, probably caused by flood and rabbit damage.
A small amount of phytoplankton was recorded and filamentous algae was not observed at the site in 2010. Over 35% of the pools were covered in aquatic plants, including both submerged (Stuckenia) and emergent species (Phragmites, Cyperus, Juncus and Typha).
The riparian zone was well vegetated with native plants and was dominated by Common Reed (Phragmites australis) under a River Red Gum canopy. The surrounding vegetation included areas of saltbush and low native woodland with gum trees over introduced grasses.
Special environmental features
None detected, although previous fish surveys at the site have collected a range of common fish species, including the Flathead Gudgeon, Dwarf Flathead Gudgeon, carp gudgeon, Common Galaxias and Australian Smelt. Further upstream, a few refuge pools also provide habitat for a threatened fish called the Mountain Galaxias (M. Hammer, Aquasave Consultants, 2009).
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.|
|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.|