Creek comprised isolated pools in autumn and a connected, non-flowing channel in spring 2016
Moderately diverse macroinvertebrate community with no rare, sensitive or flow-dependent species present
Water was fresh, clear but slightly coloured, and enriched with nutrients
Riparian vegetation consisted of a few scattered gums, prickly acacias over patches of blackberry bushes, rushes and introduced grasses
Area map
About the location
Millers Creek is a small stream in the Southern Mount Lofty Ranges that rises at an elevation of about 450 m to the south of Mount Crawford Forest and flows for about 7 km in a southerly direction, before discharging into the River Torrens about 1 km north from Gumeracha. The major land uses in the 1,754 hectare catchment upstream from the site were stock grazing (52%), irrigated horticulture (20%) and residential living (12%), with smaller areas used for other minimal uses, irrigated cropping and pastures, roads, cropping, plantation forestry, dams and nature conservation. The site sampled was located in the mid reaches of the creek upstream from Checker Hill Road, about 500 m south from Forreston.
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 significant human disturbance due to the degradation of riparian habitats and high nutrient concentrations, caused by agricultural practices in the catchment but the creek still supported a range of tolerant and generalist aquatic macroinvertebrates.
Findings
A moderately diverse community of at least 35 species of macroinvertebrates was collected or seen from the creek (16 species in autumn and 26 in spring), 7 m wide and approximately 1 m deep, in autumn and spring 2016. The creek consisted of isolated pools in autumn but a connected, although not flowing, channel in spring. The community was dominated by large numbers of introduced snails (Potamopyrgus and Physiella), and amphipods (Austrochiltonia). It also included low to moderate numbers of turbellarians, native snails, pea mussel, worms, mites, isopods, springtails, beetles, mosquitoes, chironomids, mayflies, waterbugs and caddisflies. Most macroinvertebrates recorded from the site were generalist, opportunistic and tolerant species that have a wide distribution from other organically polluted streams in the region. No rare or sensitive species were collected.
The water was fresh (salinity ranged from 182-661 mg/L), well oxygenated (65-95% saturation), clear but slightly coloured in spring, and with moderate to high concentrations of nutrients such as phosphorus (0.06-0.13 mg/L) and nitrogen (0.59-0.75 mg/L). Small patches of oil were noticed on the edge of the creek in spring.
The sediments were dominated by detritus, silt and filamentous algae, with smaller amounts of bedrock, boulder, gravel, sand and clay also present. Samples taken from below the surface were black silts and clays that released sulfide when tested and were anaerobic, or lacking oxygen, indicating they would be harsh environments for burrowing species to live in. Less than 10% of the banks showed damage caused by cattle accessing and defaecating in the bed and on the banks of the creek.
There were only small amounts of phytoplankton recorded during the year (chlorophyll a ranged from 1.9-2.2 μg/L) and filamentous algae (Cladophora and Spirogyra) covered more than 10% of the channel in both sampling seasons. More than 65% of the creek was covered by aquatic plants in spring, including the floating fern (Azolla) and patches of cumbungi (Typha) and rushes (Juncus), starwort (Callitriche), sedges (Cyperus and Isolepis), common reed (Phragmites) and the introduced watercress (Rorippa) and dock (Rumex). The narrow riparian zone consisted of a few scattered gums and prickly acacias over patches of blackberry bushes, rushes and introduced grasses. The surrounding vegetation comprised cleared cattle grazing lands with scattered gums.
Special environmental features
None identified.
Pressures and management responses
Pressures
Management responses
Widespread introduced weeds in the riparian zone at the site and upstream
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. The Board also partner with local government to deliver a number of watercourse revegetation projects across the region.
Nutrient inputs to the creek from numerous diffuse sources (potentially leading to excess growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board 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.
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Observed Condition
Expected Condition
