Burra Creek, near Worlds End
2010 Aquatic Ecosystem Condition Report
- Permanently flowing, moderately freshwater creek in autumn and spring.
- Sparse macroinvertebrate community with at least two rare species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation comprised mostly of native species.
About the location
Burra Creek is a large stream in the northern Mount Lofty Ranges. It rises north of Burra and flows in a southeasterly direction, where it ultimately connects to the River Murray to the east of Morgan. Flows generally disappear underground in the lower reaches of the creek but have occasionally extended to the river during exceptional flooding periods in the past.
The major land uses are sheep grazing and cereal cropping in the upper catchment, with minor areas used for lucerne, irrigated cropping, rural residential, orchards and recreation. Native vegetation occurs mostly along the hills, gorges and gullies in the catchment. The monitoring site was located at the end of the track off World’s End Gorge Road, about three kilometres west of Worlds End.
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 considerable evidence of human disturbance, including nutrient enrichment and fine sediment deposition, although the creek still provided an important habitat for some rare macroinvertebrate species.
A sparse community of about 24 species of macroinvertebrates was collected from the flowing creek, up to nine metres wide and over one metre deep, in autumn and spring 2010. Fast-flowing riffle habitat was present during both seasons sampled but was only extensive enough to sample in spring. The community was dominated by species tolerant to poor water quality such as amphipods (Austrochiltonia australis) and corixid waterbugs (Micronecta) in the pools and blackflies (Simulium ornatipes), chironomids (including Cricotopus and Procladius) and caddisflies (Cheumatopsyche AV2) in the riffles.
Smaller numbers of various other generalists and tolerant species were also collected, including nematodes, worms, freshwater shrimp, yabbies, beetles, biting midges, baetid mayflies, several waterbugs, odonates and leptocerid caddisflies. At least two flow-dependent species (Simulium ornatipes and Cheumatopsyche AV2) and a rare damselfly (Notosticta solida) and beetle (Laccophilus sharpi) were collected from the site. The only fish collected was the introduced mosquitofish (Gambusia).
The water was moderately fresh (salinity of 2,506 mg/L in autumn and 2,884 mg/L in spring), well oxygenated (72-103% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (0.62-0.64 mg/L) and phosphorus (0.02 mg/L).
The sediments were dominated by bedrock, boulders and algae in the riffles and detritus, silt, gravel and pebble in the still and slow-flowing pool habitats. Samples taken from below the surface were black, sulphidic and anaerobic indicating that too much organic matter had entered the creek in the past. A deposit of 5-10 cm of silt covered the creek bed in spring and no erosion was noted during either sampling period.
A small amount of phytoplankton was recorded and over 10% of the stream was covered by filamentous algae (Spirogyra) in spring. More than 35% of the site was also covered by a range of emergent aquatic plants (Phragmites, Typha, Cotula, Juncus, Isolepis, Cyperus and Bolboschoenus) in spring. The riparian zone extended over 10 metres wide and consisted of sedges, boobialla (Myoporum), acacias and River Red Gums. The surrounding vegetation was mainly native vegetation including acacias and gum trees over introduced grasses and weeds.
Special environmental features
Burra Creek provides habitat for a damselfly that has only been collected from other parts of the River Murray catchment in South Australia, and a rarely collected dytiscid beetle.
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 local government and the community have been working to address impacts by recreational activities at this site including fencing, revegetation and ongoing site maintenance.|