Finniss River, near Yundi
2010 Aquatic Ecosystem Condition Report
- Permanently wet, slow-flowing, freshwater stream in both autumn and spring.
- Moderately diverse macroinvertebrate community with many rare and sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation mostly willows and weeds.
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, northeast of Goolwa. It receives flow from Meadows, Blackfellows and Bull creeks in the upper reaches and Tookayerta Creek in the lower reach, several kilometres south of Finniss. 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 of 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 site, and the riparian zone is disturbed due to the prevalence of weeds. However, this site provides habitat for many rare and sensitive macroinvertebrates and fish species.
A moderately diverse community of about 36 species of macroinvertebrates was collected from the slow-flowing river, 21–35 metres wide and over one metre deep in places, in autumn and spring 2010. The community was dominated by tolerant species such as amphipods (Austrochiltonia australis), snails (including the introduced Physa acuta) and damselflies, and large numbers of more sensitive leptophlebiid mayflies (Koorrnonga inconspicua and Atalophlebia) were recorded in spring.
The community also included flatworms, leeches, worms, mites, beetles, mosquitoes, blackflies, chironomids, baetid and caenid mayflies, waterbugs, odonates, and caddisflies. The rare and sensitive species included the leptophlebiid mayflies and a leptocerid caddisfly (Triplectides similis); a gripopterygid stonefly (probably Dinotoperla evansi) was also seen in the small riffle habitat that was not sampled in spring. One threatened native fish called a Mountain Galaxias (Galaxias olidus) and an introduced mosquitofish (Gambusia) were also collected from the site in 2010.
The water was fresh (salinity of 344 mg/L in autumn and 985 mg/L in spring), well oxygenated (81–91% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (0.41–0.84 mg/L) and phosphorus (0.04 mg/L).
The sediments were dominated by detritus, sand, gravel and silt; samples taken from below the surface were anaerobic and sulfidic in autumn, indicating that too much organic matter had entered the river in the past. A deposit of 1–5 cm of silt covered the riverbed and over 10 metres of the bank showed signs of erosion in autumn due to flood damage.
Small growths of filamentous algae (Cladophora and Spirogyra) were recorded in both seasons sampled, and aquatic plants were particularly common in spring when they covered more than 35% of the channel. A range of floating (Azolla and Spirodela), submerged (Stuckenia pectinatus) and emergent species (Phragmites, Carex, Cyperus, Triglochin, Typha, Isolepis, Juncus, Mimulus and introduced Rorippa) were growing in the channel and on the water’s edge. The riparian zone consisted mainly of willows over weeds and introduced grasses, with a few reeds, sedges and rushes in places. The surrounding vegetation was introduced grasses, blackberries and grazed grassland.
Special environmental features
Finniss River provides habitat for several sensitive macroinvertebrates (including two species of mayfly, one stonefly and one caddisfly) and a threatened fish species (Mountain Galaxias) at the site sampled. Another threatened fish, the Climbing Galaxias, was also recorded during 2010 from a site sampled from the Finniss River near Mount Observation.
Recent fish surveys in the catchment have also recorded several additional threatened species from the main channel of the river, including the Southern Pygmy Perch, Murray Hardyhead and Congolli (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 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.|
|Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity.||The SA Murray–Darling Basin NRM Board is working with the Department for Water and the community to develop a water allocation plan and licensing system which aim to balance social, economic and environmental needs for water. The objective for providing water to the environment is to maintain and/or restore self-sustaining water-dependent ecosystems which are resilient in times of drought.|
|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.|
|Feral predatory fish (trout and redfin) (reducing ecological integrity).||Local volunteer groups are undertaking works at some sites. The SA Murray–Darling Basin NRM Board opportunistically removes pest fish during monitoring activities. Other agencies are responsible for the control of pest fish and have undertaken some awareness-raising activities throughout the region.|