Deep Creek is a small stream in the southern Mount Lofty Ranges that rises at an elevation of 260 metres to the north-west from Mosquito Hill and flows in a south-easterly direction before discharging onto the lower Currency Creek floodplain. The major land uses in the catchment are stock grazing and cropping. The monitoring site was located in the middle reaches off Deep Creek Road, about 2.5 kilometres south-east from Tooperang and 11 kilometres south-east from Mount Compass.
The creek was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure, and some changes to the way the ecosystem functions. There was evidence of human disturbance including nutrient enrichment, fine sediment deposition and weeds dominating the understorey vegetation on the banks.
Findings
A moderately diverse community of at least 19 species of macroinvertebrates was collected from the slow-flowing creek, up to 2.7 metres wide and 39 centimetres deep, in autumn 2015; the site was dry in spring. The community was dominated by moderate numbers of generalists and species tolerant to poor water quality such as amphipods (Austrochiltonia), mayflies (Cloeon) and chironomids (including Paramerina, Kiefferulus and Tanytarsus). It also included smaller numbers of mites, isopods, beetles, mosquitoes, dixids, waterbugs, stoneflies and damselflies. The only sensitive species collected was the stonefly (Dinotoperla evansi) which typically occurs in flowing habitats with good water quality; the mayfly recorded from the site is widely distributed in the state and generally considered to be tolerant to poor water quality (eg Corbin & Goonan 2010).
The water was fresh (salinity 968 mg/L), well oxygenated (70% saturated), clear and slightly coloured, and with moderate to high concentrations of nutrients such as nitrogen (0.78 mg/L) and phosphorus (0.04 mg/L).
The sediments were dominated by detritus, boulder, sand and silt, and also included smaller amounts of filamentous algae and clay. Samples taken from below the surface were grey in colour and showed no evidence that the sediments were anaerobic or lacked oxygen. Over 1 centimetre of fine silt and leaves partly covered the rocks in the streambed.
A moderate amount of phytoplankton was recorded (chlorophyll a 6.9 µg/L) and about 10% of the channel was covered with a filamentous alga (Cladophora). Extensive growths of sedges (Cyperus) and introduced grass (Paspalum) covered more than 35% of the stream. The narrow riparian zone was dominated by woody weeds (Wild Roses) and sedges, and the surrounding vegetation was an open woodland comprising native gums and shrubs over and a weedy understorey.
Special environmental values
The most notable feature of the site in 2015 was the presence of the stonefly.
Pressures and management responses
Pressures
Management responses
Livestock have direct access to some creeks, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).
Natural Resources SA Murray–Darling Basin 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 some creeks, providing minimal buffer protection from catchment landuses (reducing habitat quality).
Natural Resources SA Murray–Darling Basin recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The NRM Board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.
Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity).
A water allocation plan that guides sustainable water use in the Eastern Mount Lofty Ranges has been developed by Natural Resources SA Murray–Darling Basin, working with the community and government (particularly the Department for Environment, Water and Natural Resources (DEWNR)). The plan aims to balance social, economic and environmental water needs and is implemented through a system of water licensing and permits for water affecting activities administered by DEWNR.
A key component of the water allocation plan is to provide water to sustain the environment at an acceptable level of risk. Securing low flows for the environment is a key environmental water provision in this area, and Natural Resources SA Murray–Darling Basin is working together with DEWNR, Natural Resources Adelaide and Mount Lofty Ranges and the community to develop a program to secure low flows across the Mount Lofty Ranges. For more information on water allocation planning and associated projects go to our Water Allocation Planning web page.
In addition, this site is located in an area where the total demand for water is higher than the sustainable limits set out in the water allocation plan. Natural Resources SA Murray–Darling Basin is monitoring the situation and will work with the community to develop solutions for managing high water demand where required.
Widespread introduced trees and weeds in riparian zones (reducing habitat quality).
Natural Resources SA Murray–Darling Basin recognises the limitations of available funds relative to the scale of the degradation caused by introduced trees and weeds. It 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. It actively seeks funding opportunities for weed control; most opportunities are for locations where biodiversity outcomes can be achieved.