Tributary of the Hindmarsh River, 2 km east from Hindmarsh Tiers
2011 Aquatic Ecosystem Condition Report
- Permanently wet, slow-flowing, freshwater creek in autumn and spring 2011
- Moderately diverse macroinvertebrate community with several rare and sensitive species
- Obvious signs of moderate nutrient enrichment
- Riparian vegetation includes a range of native and introduced plants
- Some areas of bank erosion and fine sediment deposits in the creek
About the location
Tributary of the Hindmarsh River is a small stream in the Southern Mount Lofty Ranges that rises south from Woodcone Hill and flows in a southerly direction before discharging into the Hindmarsh River, near Mount Billy Conservation Park on the Fleurieu Peninsula. The monitoring site was located on a track near ‘Culdee’ off Haskett Road, about 2 km east from Hindmarsh Tiers. The major land uses in the 202 hectare catchment are stock grazing and remnant native vegetation, with smaller areas of forestry, irrigated grasses, rural residential living and roads.
The creek 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, a degraded riparian zone, fine sediment deposited in the creek and some bank erosion evident. Despite this, the stream provided habitat for some rare and sensitive species.
A moderately diverse community of at least 37 species of macroinvertebrates was collected from the slightly flowing creek, 0.8-3.5 m wide and up to 28 cm deep, in autumn and spring 2011. The community was dominated by generalists, tolerant and sensitive species, including amphipods, hypogastrurid springtails, mosquitoes, chironomids and stoneflies. It also included smaller numbers of limpets, native and introduced snails, mites, yabbies, beetles, biting midges, various types of flies, mayflies, waterbugs, odonates and stoneflies. The site was unusual because it lacked any caddisflies, despite the apparent presence of suitable habitats. Several rare or sensitive species were collected, including a chironomid (Podonomopsis), mayfly (Thraulophlebia inconspicua) and two stoneflies (Riekoperla naso and Austrocerca tasmanica); they were mostly recorded in spring. No fish were seen at the site in 2011.
The water was fresh (salinity ranged from 370-428 mg/L), well oxygenated (112-128% saturated), slightly turbid in spring but clear in autumn, and with high concentrations of nutrients such as nitrogen (1.4-1.8 mg/L) and phosphorus (0.07-0.1 mg/L).
The sediments were dominated by detritus and silt, with sand, clay and algae also present. Samples taken from below the surface were grey in colour and showed no evidence that the sediments were anaerobic or lacked oxygen. A deposit of 1-5 cm of silt covered the channel and about 10 m of bank showed signs of erosion in spring due to recent flood damage and horses accessing the edges of the creek.
A moderate amount of phytoplankton was recorded in spring, when filamentous algae (including Cladophora) covered nearly 10% of the site. A similar area of the channel was covered by a range of submerged (Chara, Myriophyllum and Potamogeton) and emergent plants (Eleocharis, Juncus, introduced Rorippa, Rumex, Triglochin and Isolepis). The riparian vegetation was limited in extent and consisted of River Red Gums, introduced willows and ash trees over rushes, introduced grasses and weeds. The surrounding vegetation was grazing land with a few scattered gum trees located towards the creekline.
Special environmental features
This small, freshwater stream provides habitat for at least four rare or sensitive species of macroinvertebrates.
Pressures and management responses
|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.|
|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.|
|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.|
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.