Permanent flowing stream in autumn and spring 2016
A moderately diverse macroinvertebrate community with several rare, sensitive and/or flow-dependent species present
Water was fresh, clear but coloured, and showing signs of nutrient enrichment
Riparian vegetation consisted of native vegetation over introduced grasses
Area map
About the location
The Deep Creek is a moderately sized stream in the Southern Mount Lofty Ranges that rises west from Parawa and flows southwards, where it eventually discharges into Deep Creek Cove in the Southern Ocean. The monitoring site was located on an access track in the centre of Deep Creek Conservation Park, about 1.5 km west from Tapanappa Hill and 2 km south from the Park headquarters. The major land uses in the 3,104 hectare catchment are stock grazing (47%), conservation and other minimal uses (32%) and forestry (13%), with smaller areas used for irrigated cropping and horticulture, dams, roads, cropping and rural residential living.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance due to nutrient enrichment but the stream provides habitat for many rare, sensitive and flow-dependent species of macroinvertebrates.
Findings
A moderately diverse community of at least 35 species of macroinvertebrates was collected from the creek (23 species in autumn and 23 in spring), more than 3 m wide and up to 40 cm deep, in autumn and spring 2016. The creek consisted of still to slow-flowing pools that were connected by shallow, fast-flowing riffle habitats in both sampling seasons. The community was dominated by large numbers of amphipods (Austrochiltonia australis) and leptophlebiid mayflies (Nousia fuscula and Thraulophlebia inconspicua). Smaller numbers of hydrobiid snails (including the introduced Potamopyrgus), worms, mites, marsh beetles, dixid flies, biting midges, blackfly larvae (Austrosimulium furiosum), chironomids, waterbugs, dragonflies, stoneflies and caddisflies were also present. Numerous crayfish holes were seen in the wet banks of the creek, which were assumed to be marron burrows. A wide range of rare, sensitive and/or flow-dependent species were recorded, including the stoneflies (Illiesoperla mayi, and Dinotoperla evansi), caddisflies (Taschorema evansi and Ulmerochorema membrum) and the above-listed blackflies and leptophlebiid mayflies.
The water was fresh (salinity ranged from 576-665 mg/L), well oxygenated (74-80% saturation), clear but slightly coloured in autumn, and with moderate to high concentrations of nutrients such as phosphorus (0.04-0.05 mg/L) and nitrogen (1.17-1.18 mg/L).
In the slow-flowing pools the sediments were dominated by detritus with small amounts of sand, silt, clay, cobbles and pebbles. The riffles were dominated by boulders, cobbles and pebbles, with some finer sediments also present. Samples taken from below the surface were mostly grey clays and silts and showed no signs that the sediments were anaerobic or sulfidic. There was some evidence of bank erosion (<10m) due to damage from higher flows in the past.
There was only a small amount of phytoplankton present (chlorophyll a ranged from <0.1-0.68 μg/L) but no filamentous algae was present in either season. Aquatic plants covered over 10% of the creek and included Potamogeton, Hydrocotyle, Isolepis, Phragmites and Triglochin. The riparian zone consisted of native vegetation that was dominated by gums over tea-tree shrubs and bracken, with some introduced grasses also present. The surrounding vegetation near the creek comprised dense native woodland within The Deep Creek National Park.
Special environmental features
The Deep Creek consists of a permanently flowing, freshwater, riffle-pool sequence stream that supports a wide range of rare, sensitive and flow-dependent species.
Pressures and management responses
Pressures
Management responses
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.
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.
Insufficient natural water flows in the creek resulting from water extraction and climate variability
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.
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.
Observed Condition
Expected Condition
