North Para River, d/s Penrice Gauge Station
2013 Aquatic Ecosystem Condition Report
- Dry in autumn and non-flowing channel in spring 2013
- Moderately diverse macroinvertebrate community in spring with two significant species recorded
- Water was moderately fresh, clear and enriched with nutrients
- Riparian vegetation consisted of scattered River Red Gums over introduced grasses and weeds
About the location
The North Para River is one of the largest streams in the Northern Mount Lofty Ranges. It rises at an elevation of about 450 m in the Flaxman Valley near Eden Valley and flows north towards Angaston, where the river flows south-east through Nuriootpa, Tanunda and Rosedale before eventually joining with the South Para River at Gawler to form the Gawler River. The major land uses in the 11,680 hectare catchment were stock grazing, irrigated vines and cropping, with small areas also used for other minimal uses, roads, dams, residential living and mines/quarries. The site was located downstream from Stockwell Road and the Penrice gauge station, about 3 km north from Penrice and 4 km east from Nuriootpa.
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 due to nutrient enrichment and the presence of woody and herbaceous weeds in the riparian zone but the river still supported a wide range of aquatic species. If nutrient levels remain high or increase any further, then the environmental condition of this site will inevitably decline in the future.
A moderately diverse community of at least 25 species of macroinvertebrates was collected from the 3.4 m wide, 30 cm deep creek in spring; the creek was dry in autumn. The creek consisted of a non-flowing river channel that appeared to be drying when it was sampled. The community was dominated by moderate numbers of chironomids (Procladius, Tanytarsus and Chironomus) and included low numbers of native and introduced snails (including Physa), limpets, leeches, worms, mites, beetles, long-legged flies (Family Dolichopodidae), mayflies, waterbugs, damselflies, dragonflies and caddisflies. The presence of yabby claws indicated that this burrowing species was also present at the site. Most of these were generalist, opportunistic and tolerant species that are commonly found from organically enriched streams in the region. The only sensitive species recorded were the mayflies (Atalophlebia australis and Thraulophlebia inconspicua) which typically occur in flowing-water habitats but may persist for some time in streams after flows have ceased.
The water was moderately fresh (salinity of 1,229 mg/L), moderately well oxygenated (52% saturation), clear, and with high concentrations of nutrients such as phosphorus (0.07 mg/L) and nitrogen (1.7 mg/L).
The sediments were dominated by detritus, silt and bedrock, with smaller amounts of cobble, boulder, gravel, sand and clay also present; samples taken from below the surface were anaerobic grey silts that released sulphide when tested in spring, indicating that the sediments lacked oxygen when the river was wet at this site. There was a minor amount of bank erosion noted in spring, when about 10m of bank showed evidence of recent flood damage. The only animal droppings seen near the river were from kangaroos and emus.
Only a small amount of phytoplankton was recorded from the river (chlorophyll a 1.03 μg/L) and no filamentous algae was seen at the site in 2013. More than 35% of the channel was covered by a range of aquatic plants, including sedges (Cyperus, Schoenoplectus and Eleocharis), rushes (Juncus), dock (Rumex), water ribbons (Triglochin) and cumbungi (Typha); the dry autumn channel also included dead sea tassels (Ruppia) and sedges (Bolboschoenus). The riparian zone extended over 5 m wide and was dominated by scattered River Red Gums and introduced ash and olive trees growing over introduced grasses, fennel and other weedy species. The surrounding vegetation near the creek comprised open eucalypt woodland with a weedy understorey.
Special environmental features
The most significant environmental assets recorded from the site in 2013 were the presence of the two mayfly species which typically occur among flowing riffle habitats elsewhere in the region. The rich macrophyte community also shows that a wide range of aquatic plants grow in the river when it holds water.
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.|
|Large nutrient inputs to the creek from numerous diffuse sources (leading to extensive growth of algae and aquatic weeds)||The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes working with industry and landholders to ensure efficient use of fertilisers and discuss ways to reduce runoff of nutrients into waterways.|
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.