Riparian vegetation mostly willows, introduced grasses and weeds
Area map
About the location
Finniss River is a large stream in the southern Mount Lofty Ranges that rises east of Yundi and flows in an easterly direction where it eventually discharges into the Lower Murray, north-east from Goolwa. The major land uses are cattle and sheep grazing. The monitoring site was located on the ford at the southern end of Mount Magnificent Road near the junction with Enterprise Road, about three kilometres east from Yundi.
The river was given a good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. However, much of the catchment upstream is cleared and grazed, which contributes large nutrient and fine sediment loads to the stream, and the riparian zone at the site has been highly disturbed and comprises weedy species. Despite this, instream habitats support many rare and sensitive macroinvertebrates, indicating that the aquatic habitats at the site have not been severely degraded by catchment pressures during the sampling period reported here.
Findings
A diverse community of at least 50 species of macroinvertebrates (33 in autumn and 32 in spring) was collected or seen from the flowing river, 2-2.4 metres wide and over 34 centimetres deep in places, in autumn and spring 2015. The majority of the stream comprised slow to non-flowing pool habitats that were connected by small areas of fast-flowing riffles. The community was dominated by tolerant species such as amphipods (Austrochiltonia australis) and snails (including introduced Potamopyrgus and Physiella). The community also included a range of flatworms, freshwater limpets, pea mussels, leeches, worms, isopods, yabbies, beetles, chironomids, dixid flies, mosquitoes (Culex), biting midges (Bezzia), waterbugs, odonates, mayflies and caddisflies. A rich assemblage of caddisflies was recorded from the site, including three species of Triplectides (T. australis, T. australicus and the flow-dependent T. similis), Lectrides varians, Hellyethira simplex, Notalina species, and some Hydroptila larvae were also seen from the riffle habitat in autumn. The site also provided habitat for five mayflies, including sensitive leptophlebiids (Atalophlebia australasica, Atalophlebia australis and Thraulophlebia inconspicua) and two more generalist taxa (Cloeon and Tasmanocoenis). Another two flow-dependent taxa (blackflies and gripopterygid stoneflies) were also seen in the small riffle habitats in autumn.
The water was fresh (salinity of 721 mg/L in autumn and 763 mg/L in spring), well oxygenated (44-77% saturation), clear and slightly coloured, and with moderate to high concentrations of nutrients such as nitrogen (0.60-0.92 mg/L) and phosphorus (0.04-0.05 mg/L).
The sediments were dominated by detritus and sand, with smaller amounts of gravel and silt; samples taken from below the surface were black, anaerobic and sulphidic in autumn, indicating that too much organic matter had entered the river. A deposit of 1-5 centimetres of silt covered the riverbed but no bank erosion was noted despite the presence of cattle droppings on the edges of the stream.
Small growths of phytoplankton (chlorophyll a ranged from 1.4-5.6 µg/L) were recorded and filamentous algae covered more than 10% of the channel in both seasons sampled (Spirogyra in autumn and Cladophora in spring). Over 65% of the streambed and edges were covered by a range of aquatic plants, including floating (Azolla and Spirodela), submerged (Callitriche and Myriophyllum) and emergent species (Cyperus, Isolepis, Juncus, Phragmites, Triglochin, Typha and introduced Rorippa and Rumex). The narrow (<5 metres wide) riparian zone consisted mainly of willows over weeds and introduced grasses, with a few reeds, sedges, and rushes and introduced blackberries in places. The surrounding vegetation was cattle grazing land with a few scattered gum trees remaining in the local landscape.
Special environmental values
Finniss River provides habitat for several sensitive macroinvertebrates (including mayflies, caddisflies and stoneflies) and a wide range of tolerant and generalist invertebrates and plants.
Mountain galaxias, a native fish species identified as vulnerable in the 2009 ‘Action plan for South Australian freshwater fishes’, has been found at this site within the last five years (Nick Whiterod, Aquasave Consultants, pers. comm.)
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.
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.
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.