Tributary of the Hindmarsh River, near Cloverdale
2011 Aquatic Ecosystem Condition Report
- Permanently wet, flowing, freshwater creek in autumn and spring 2011
- Moderately diverse macroinvertebrate community with many rare, sensitive and flow-dependent species
- Obvious signs of moderate to gross nutrient enrichment
- Riparian vegetation dominated by introduced grasses and blackberries
- Areas of creek affected by silt deposits and bank erosion.
About the location
Tributary of Hindmarsh River is a small stream in the Southern Mount Lofty Ranges that rises near Spring Mount and flows in a northerly direction into the Hindmarsh River near ‘Cloverdale’. The monitoring site was located on a track off Hindmarsh Tiers Road, about 1.5 kilometres WNW from Hindmarsh Tiers on the Fleurieu Peninsula. The major land uses in the 2,132 hectare catchment are stock grazing and remnant native vegetation, with smaller areas used for irrigated grasses and crops, forestry and rural residential living.
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, degraded riparian habitats, fine sediment deposited in the creek and areas of bank erosion. Despite this, the stream still provided habitat for a number of rare and sensitive macroinvertebrate species.
A moderately diverse community of at least 35 species of macroinvertebrates was collected from the flowing creek, 2.1-2.4 m wide and up to 58 cm deep, in autumn and spring 2011. The creek consisted of a slightly flowing channel in autumn but included areas of still and moderately fast-flowing channel habitat in spring. The community was dominated by generalists and species tolerant to poor water quality such as amphipods (Austrochiltonia), blackflies, chironomids and hydrobiid snails. It also included smaller numbers of limpets, introduced (Physa and Potamopyrgus) and native snails (Angrobia), worms, freshwater shrimp, springtails, beetles, dixids, mayflies, waterbugs, odonates, stoneflies and caddisflies. Several rare and sensitive species were collected, including blackfly larvae (Austrosimulium furiosum), mayflies (Atalophlebia australasica and Thraulophlebia inconspicua), and a stonefly (Illiesoperla mayi) and caddisfly (Taschorema evansi). The site also provided habitat for a range of species that are normally associated with flowing water, including a blackfly (Simulium ornatipes), dytiscid beetle (Platynectes decempunctatus), chironomid (Rheotanytarsus), and the above-listed rare and sensitive species. The only fish collected at the site was a single threatened native species called Mountain Galaxias (Galaxias olidus).
The water was fresh (salinity ranged from 780-869 mg/L), well oxygenated (107-113% saturated), slightly coloured and turbid in spring, and with moderate to high concentrations of nutrients such as nitrogen (0.56-0.69 mg/L) and phosphorus (0.04 mg/L).
The sediments were dominated by detritus and silt, with sand, gravel and clay also present. Samples taken from below the surface were slightly black in colour, indicating that the sediments had recently been anaerobic or lacked oxygen. A large deposit of silt, over 10 cm deep, covered the creekbed in autumn but only about 1 cm remained when the site was surveyed again in spring; winter rains has presumably transported most of the sediment further downstream. About 10 m of bank showed evidence of erosion due to flood damage and cattle accessing the edges of the creek.
Over 10% of the creek was covered by filamentous algae (including Cladophora) in autumn but none was recorded in spring. Up to 65% of the channel was covered by an extensive growth of introduced watercress (Rorippa) and patches of several other types of aquatic plants (Myriophyllum, Eleocharis, Juncus and Rumex). The narrow riparian zone consisted of a few River Red Gums over introduced grasses, blackberries and dock. The surrounding vegetation was cleared, dairy cattle grazing land and only a few isolated gum trees remained along the roadside in the local landscape.
Special environmental features
The presence of permanently flowing habitats supports a wide range of aquatic species, including numerous rare, sensitive and flow-dependent macroinvertebrates and one state-listed threatened native fish species.
Pressures and management responses
|Insufficient natural water flows in the creek resulting from water extraction and climate variability (reducing ecological integrity).||Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.|
|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.|
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.