North Para River, Rowland Flat
2011 Aquatic Ecosystem Condition Report
- Permanently wet, flowing, freshwater stream in autumn and spring 2011
- Diverse macroinvertebrate community with a few rare and sensitive species
- Obvious signs of gross nutrient enrichment
- Riparian vegetation dominated by River Red Gums over woody and herbaceous weeds.
About the location
The North Para River is a large stream in the Southern Mount Lofty Ranges that rises south from Kaiserstuhl Conservation Park and flows north towards Angaston, then turns west towards Nuriootpa and finally turns south-west, where it eventually joins with the South Para River to form the Gawler River in Gawler. The monitoring site was located on Rowland Flat Road, about 1 km north from Rowland Flat in the Barossa Valley. The major land uses in the 35,950 hectare catchment are stock grazing and irrigated vines, with smaller areas used for a range of other agricultural activities, residential living and remnant native vegetation. The townships of Tanunda, Nuriootpa and Angaston and the Nuriootpa effluent ponds are all located upstream from the site.
The river 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 and degraded riparian vegetation but the stream still provided habitat for some rare and sensitive macroinvertebrate species.
A diverse community of at least 48 species of macroinvertebrates was collected from the flowing river, 6.2-7.1 m wide and up to 33 cm deep, in autumn and spring 2011. The river consisted of pool habitats connected by extensive areas of shallow, flowing riffle habitats. The community was dominated by generalists and species tolerant to poor water quality such as chironomids, mayflies, blackflies and amphipods (Austrochiltonia). The mayflies (Cloeon and Tasmanocoenis) represented the two most tolerant types that occur in South Australia. The community also included smaller numbers of flatworms, native and introduced snails, worms, mites, freshwater shrimp, yabbies, springtails, beetles, mosquitoes, biting midges, sciomyzids, waterbugs, odonates, stoneflies and caddisflies. The only sensitive or rare species collected included a leptophlebiid mayfly (Atalophlebia australasica), hydrobiosid caddisfly (Ulmerochorema membrum) and an unidentified stonefly. Several species normally associated with flowing habitats were also recorded, including a beetle (Platynectes decempunctatus), blackfly (Simulium ornatipes), chironomid (Rheotanytarsus), caddisfly (Cheumatopsyche sp. 2), and the above-listed rare and sensitive species. No fish were seen at the site in 2011.
The water was fresh to moderately fresh (salinity ranged from 915-1,337 mg/L), well oxygenated (110-136% saturated), clear, and with high concentrations of nutrients such as nitrogen (2.24-3.35 mg/L) and phosphorus (0.9-1.5 mg/L).
The sediments were dominated by detritus, cobble, bedrock and algae in the slow-flowing edge habitats and boulder, cobble and algae in the fast-flowing riffles. Samples taken from below the surface were slightly blackened in colour but otherwise showed no evidence that the sediments had recently been anaerobic or lacking in oxygen. Only small deposits of silt, about 1 cm deep, covered the streambed and no significant areas of bank erosion was noted at the site.
A large amount of phytoplankton was present during both surveys carried out and extensive growths of filamentous algae (including Cladophora and Spirogyra) covered over 35% of the channel in spring. A similar area was covered by a range of emergent plants (Cyperus, Bolboschoenus, Juncus, Phragmites, Rumex and Typha). The narrow riparian zone was dominated by River Red Gums, willows and ash trees over introduced grasses, weeds (including olives and wild roses) and emergent macrophytes (reeds, sedges and rushes). The surrounding vegetation included a vineyard and patches of gum trees over introduced grasses.
Special environmental features
The North Para River near Rowland Flat provides permanently flowing, freshwater habitats that support a few rare, sensitive and flow-dependent species.
Pressures and management responses
|Widespread introduced weeds in the riparian zone at the site and upstream (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.|
|Livestock having direct access at the site and upstream (causing sediment erosion and adding excessive nutrients).||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.|
|Limited riparian zone vegetation at the creek and upstream (reducing habitat quality, increasing sediment erosion).||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion.|
|Wastewater discharges to the creek, adding excessive nutrients and organic matter (leading to algal growth and aquatic weeds).|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.