Logan Creek, near Logan Gap
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 gross nutrient enrichment.
- Riparian vegetation limited to introduced grasses and weeds.
About the location
Logan Creek is a small stream in the Mid North region. It drains the north-eastern side of the Tothill Ranges and flows in a northerly direction before discharging into Burra Creek. The major land use is sheep grazing.
The monitoring site was located on a track off the Koo-owie Gap Road, about one kilometre north-east of Logan Gap.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance, including nutrient enrichment, fine sediment deposition and degraded riparian vegetation.
A sparse community of about 14 species of macroinvertebrates was collected from isolated pools, up to two metres wide and 35 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by species tolerant to poor water quality such as mosquitoes and chironomids (including Chironomus and Cricotopus). It also included smaller numbers of mites, amphipods, beetles, brineflies and waterbugs. No rare or sensitive species were found and the site was notable for the absence of any mayflies, stoneflies, caddisflies or odonates.
The water was saline (salinity of 4,719 mg/L), well oxygenated (118% saturation) and clear, with high concentrations of nutrients such as nitrogen (1.61 mg/L) and phosphorus (0.1 mg/L.
The sediments were dominated by detritus and silt; samples taken from below the surface were blackened, sulphidic and anaerobic, indicating that too much organic matter had entered the creek in the past. A deposit of 1–5 centimetres of silt covered the creekbed in places.
A large amount of phytoplankton was recorded and filamentous algae (Spirogyra) covered more than 10% of the pools in spring. Over 65% of the site was covered by aquatic plants, including Common Reed (Phragmites australis), Sea Club-rush (Bolboschoenus caldwellii) and sedges (Cyperus).
The riparian zone consisted of introduced grasses and thistles. No trees or shrubs were present. The surrounding vegetation was cropping and grazing land.
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.|