Reedy Creek, near Palmer
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment and salinity.
- Extensive invasion by weeds.
- No macroinvertebrates sensitive to pollution were found.
- Excessive growths of algae and aquatic plants.
- Creek provides habitat for a threatened fish species.
About the location
Reedy Creek is a permanent creek formed from several smaller streams that rise in the eastern Mount Lofty Ranges around Mount Torrens, Tungkillo and Palmer. It flows through mainly sheep grazing and cropping land to the River Murray, about four kilometres south of Mannum.
The site selected for monitoring was located in the mid reaches of the creek, upstream from the Palmer to Murray Bridge road and four kilometres south of Palmer, near Hillydale.
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 stream was saline, with very high nutrient levels and heavy infestations of weeds along its banks.
The creek was made up of still, connected pools when samples were taken at the site in November 2008. The channel was only about four metres wide and most pools were less than 25 centimetres deep.
A moderately diverse community of 39 species of macroinvertebrates was collected. The most common species were chironomids and culicine mosquito larvae, which are tolerant to high nutrient levels and poor water quality. No sensitive or rare species were found.
The water was saline (salinity of 5,500 mg/L), poorly oxygenated (37% saturation), and slightly coloured and cloudy, or turbid. It contained high concentrations of nutrients such as nitrogen (1.8 mg/L), phosphorus (0.1 mg/L) and organic carbon (27 mg/L).
Large amounts of phytoplankton were dispersed in the water, and green filamentous algae covered up to 35% of the creek's surface. Cumbungi (Typha) and Common Reeds (Phragmites australis) grew in the channel, as well as several smaller sedges, rushes and herbaceous plants.
Detritus, cobbles and fine silt made up the creekbed; the sediments were anaerobic, another indication that too much organic material had entered the creek in the past. Some slumping was evident along the streambanks.
The riparian zone was covered with River Red Gums, Melaleuca paperbarks, rushes (Juncus), introduced Pepper Trees and a wide range of weeds and grasses. Beyond this area, the landscape was dominated by cereal crops and pastures.
Special environmental features
None detected at the site in 2008 but the creek provides habitat for a threatened fish called the Mountain Galaxias and several other native fish species (e.g. Dwarf Flathead Gudgeon, Flathead Gudgeon, carp gudgeon, Common Galaxias and Australian Smelt); the latter occur in the lower reaches of the creek (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 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.|
|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.|