Greenock Creek, Roenfeldt Rd
2013 Aquatic Ecosystem Condition Report
- Isolated pools present in autumn and connected flowing creek in spring 2013
- Moderately diverse macroinvertebrate community with no rare, sensitive or flow-dependent species recorded
- Water was moderately fresh to saline and enriched with nutrients
- Riparian vegetation consisted of reeds and a few scattered gums
About the location
Greenock Creek is a small stream in the Northern Mount Lofty Ranges that rises at an elevation of about 380 m east from the Nain Ranges and flows in a southerly direction before eventually discharging into the North Para River near Rosedale. The major land uses in the 2,777 hectare catchment were cropping (35%), irrigated vines (33%) and stock grazing (18%), with smaller areas used for residential living, other minimal uses, roads, industrial uses and dams. The site was located near ‘Willowcroft’ off Roenfeldt Road, about 1 km south from Greenock.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and function. There was evidence of human disturbance due to nutrient enrichment, high salinity, degraded riparian zones and the extent of bank damage recorded at the site sampled in 2013.
A moderately diverse community of at least 21 species of macroinvertebrates was collected or seen from the creek (12 species in autumn and 16 in spring), 10-12 m wide and over 1 m deep in places, in autumn and spring 2013. The creek consisted of isolated, deep pools in autumn but comprised a connected, slow-flowing channel in spring. The community was dominated by moderate numbers of amphipods (Austrochiltonia) and springtails, and included low numbers of mites, shrimp, yabbies, springtails, dytiscid beetles, biting midges, soldierflies, chironomids waterbugs, damselflies and caddisflies. These are all either generalist, opportunistic or tolerant species that have a widespread distribution in the region, particularly from organically polluted streams. No rare or sensitive species were recorded, and there was insufficient flowing habitat present for any flow-dependent species to be able to colonise and persist in the creek during 2013. Many macroinvertebrates with a wide distribution in the region were missing from this stream, including worms, snails, mayflies, stoneflies, dragonflies and a wider range of flies, waterbugs and caddisflies; the elevated salinity in spring probably contributed to the lack of many of these groups. The only fish recorded at the site was the introduced pest species called mosquitofish (Gambusia) that were seen in low numbers during the spring survey.
The water was moderately fresh to saline (salinity ranged from 2,755-4,498 mg/L), well oxygenated (101-103% saturation), slightly turbid and coloured in autumn but clear in spring, and with high concentrations of nutrients such as phosphorus (0.03-0.15 mg/L) and nitrogen (0.70-1.93 mg/L).
The sediments were dominated by detritus, silt and clay, with smaller amounts of sand and bedrock also present; samples taken from below the surface were grey silts and sands, and showed no evidence to indicate that the sediments were occasionally anaerobic or lacking in oxygen. There was no evidence of any stock or animal droppings seen in the vicinity of the creek despite over 50% of the site being affected by significant bank erosion; presumably this was caused by recent flood damage of soft, erodible banks.
There was a large amount of phytoplankton present (chlorophyll a ranged from 5-34 μg/L) but no sign of any significant growths of filamentous algae was seen at the site during 2013. Over 65% of the channel was covered by an extensive growth of Common Reed (Phragmites australis) and a few patches of rush (Juncus). The riparian zone only extended a few metres wide in places and was comprised dense stands of reeds with a few scattered gum trees and wattles. The surrounding vegetation near the creek comprised a few gums trees among cleared sheep grazing and cereal cropping land, and vineyards in the local landscape.
Special environmental features
Pressures and management responses
|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.|
|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.