Tanunda Creek, near Bethany
2016 Aquatic Ecosystem Condition Report
Nearly dry in autumn and a flowing creek in spring 2016
Moderately diverse macroinvertebrate community with a few sensitive and flow-dependent species recorded
Water was fresh, clear but strongly coloured, and moderately enriched with nutrients
Riparian vegetation mostly consisted of River Red Gums and a few pine trees over introduced grasses
About the location
Tanunda Creek is a small to moderately sized stream which rises in the Kaiserstuhl Conservation Park in the Barossa Valley and flows occasionally, draining west towards Bethany before disappearing underground in the North Para River catchment. The major land uses in the 2,355 hectare catchment upstream from the site sampled included grazing modified pastures (45%), other minimal uses (25%) and nature conservation (17%), with smaller areas of irrigated horticulture, roads, dams, plantation forestry, residential living, and cropping also present. The site selected for monitoring was located upstream from Bethany Reserve and the ford on Bethany Road.
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 due to the extent of riparian disturbance of the understorey vegetation and nutrient enrichment. However, the stream also provides habitat for a few sensitive and flow-dependent macroinvertebrates.
A moderately diverse community of at least 37 species of macroinvertebrates was collected from the 6 m wide, 45 cm deep creek in spring; the stream was dry in autumn. The creek consisted of small isolated pools in autumn, too small to sample, but a flowing channel with riffle habitat was present in spring. The community was not dominated by any species but included low to moderate numbers of introduced and native snails (Potamopyrgus, Physiella and Glyptophysa), limpets, amphipods, mites, beetles, mosquitoes, biting midges, blackflies (Simulium ornatipes), chironomids, mayflies (including Atalophlebia australasica and Thraulophlebia inconspicua), waterbugs, a damselfly and a dragonfly, and caddisflies (including Ulmerochorema). Most were tolerant and generalist species that have a wide distribution from organically enriched streams elsewhere in the State. The only sensitive and/or flow-dependent species recorded were the above-listed blackfly, caddisfly and mayflies.
The water was fresh (salinity 316-578 mg/L), with low oxygen concentrations (44-48% saturation), clear but strongly coloured in autumn when it was just a small isolated pool, and with moderate to high concentrations of nutrients such as phosphorus (0.02 mg/L) and nitrogen (0.78 mg/L). Small patches of oils were also noticed on the edge of the creek in spring.
The sediments were dominated by detritus, boulders and cobbles in the edge habitat and cobbles and detritus in the riffle habitat. Small amounts of pebbles, gravel, sand, silt, clay and algae were also present. Samples taken from below the surface were grey sands, silts and clays that were not sulfidic or anaerobic during either season. There was some bank erosion (<10%) noted at the site which appeared to be related to recreational use of the nearby park and higher flows during recent storm events.
No phytoplankton was detected when sampled (chlorophyll a of <0.1 μg/L) but small patches of a filamentous alga (Spirogyra) covered nearly 10% of the channel in spring. A slightly larger area was covered by the aquatic plants Cyperus and Rumex. The narrow riparian zone was dominated by a line of River Red Gums and a few pine trees over introduced grasses. The surrounding vegetation comprised cleared land with a few scattered gums, vineyards and lawns surrounding the carpark associated with the recreational park.
Special environmental features
The most significant feature of this creek was that it supported a moderately diverse range of species, including a few sensitive and flow-dependent macroinvertebrates despite being dry or drying during the warmer months of the year.
Pressures and 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.
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.