North Para River, Mt McKenzie G.S.
2013 Aquatic Ecosystem Condition Report
- Permanently wet with isolated pools in autumn and spring 2013
- Moderately diverse macroinvertebrate community with no rare, sensitive or flow-dependent species present
- Water was moderately fresh, slightly turbid and coloured, and enriched with nutrients
- Riparian vegetation consisted of a few gums trees over sedges and introduced grasses
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 4,477 hectare catchment were stock grazing (65%), irrigated vines (14%) and cropping (13%), with small areas also used for other minimal uses, roads, dams, residential living and mines. The site was located at the Mt McKenzie gauge station off a track from the Mount Pleasant to Angaston Road, about 7 km south-south-east from Angaston.
The river was given a Poor rating because the site sampled showed evidence of relatively major changes in ecosystem structure and function. There was evidence of human disturbance due to the high nutrient concentrations and indicators of enrichment (eg extent of aquatic plant growth, abundance of phytoplankton, presence of filamentous algae), and the degraded riparian zone. The aquatic life was restricted to tolerant and generalist species that are often found together from other organically enriched streams in the region.
A moderately diverse community of at least 27 species of macroinvertebrates was collected or seen from the river (15 species in autumn and 22 in spring), 4.9-5.5 m wide and up to 55 cm deep, in autumn and spring 2013. The river consisted of isolated pool habitats in autumn and a connected, slow-flowing channel in spring. The community was dominated by moderate numbers of amphipods (Austrochiltonia), waterbugs (Micronecta), baetid mayflies (Cloeon) and chironomids (including Procladius and Chironomus), and included smaller numbers of limpets, native and introduced snails (including Physa), worms, mites, shrimp, yabbies, springtails, beetles, biting midges, mosquitoes, marsh flies, brine-flies, other waterbugs, dragonflies and caddisflies. These comprised generalist, opportunistic and tolerant species that have a wide distribution in the region and are capable of surviving in organically polluted waters. No rare, sensitive or flow-dependent species were recorded from the site in 2013. The only fish collected and seen at the site were mosquitofish (Gambusia), an introduced pest species that is often able to survive in streams with poor water quality.
The water was moderately fresh (salinity ranged from 1,556-2,815 mg/L), well oxygenated (101-142% saturation), slightly turbid and coloured, and with very high concentrations of nutrients such as phosphorus (0.08-0.28 mg/L) and nitrogen (1.77-3.66 mg/L).
The sediments were dominated by bedrock, gravel and detritus, with smaller amounts of pebble, silt, cobble and sand also present; samples taken from below the surface were grey sands that released sulphide when tested in spring, indicating that the sediments were occasionally anaerobic or lacking in oxygen. Over 1 cm of fine silt covered the bed of the river in spring, suggesting that large sediment loads were mobilised and deposited in the river during recent winter floods. There was no evidence of any significant bank erosion at the site but the presence of kangaroo and sheep droppings on the banks, highlights the potential for damage to occur in the future under current management practices.
There was a large amount of phytoplankton present in the river (chlorophyll a ranged from 15-90 μg/L) and cyanobacteria or blue-green algae was particularly abundant (chlorophyll b 21 μg/L) during the low flow autumn period. Filamentous algae (mostly Spirogyra) was only seen in spring, when it covered less than 10% of the site. Over 35% of the channel was covered by a range of aquatic plants, including sedges (Bolboschoenus, Schoenoplectus and Cyperus), cumbungi (Typha), water ribbons (Triglochin) and rushes (Juncus). The riparian zone extended more than 5 m wide on both banks and comprised a few large scattered River Red Gum trees over sedges, rushes, and various weeds and introduced grasses. The surrounding vegetation near the creek comprised a few remnant gums among cleared sheep grazing paddocks.
Special environmental features
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.|
|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.