Henry Creek is a small natural stream in the upper South East that extends for only about three kilometres until it meets Henry Creek Road, whereupon the stream has been turned into a straight channel or drain as it passes downstream next to the road. It joins with the Upper South East drainage scheme, via Taratap Drain, and drains into the Tilley Swamp watercourse and then into Morella Basin, Salt Creek and eventually the Coorong during very wet years.
The primary function of Henry Creek is to remove surface water and drain saline groundwater to improve agricultural productivity in the region (Department for Water 2010). The creek is not expected to be in a highly rated aquatic ecosystemcondition, although it does provide significant habitat for many aquatic species in the region.
The major land uses are grazing and large areas of remnant native vegetation. The monitoring site was located near the junction of Henry Creek Road and Litigation Lane, about 60 kilometres south-west from Keith.
The creek was given a fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. Therewas evidence of human disturbance, including nutrient enrichment and fine sediment deposition in the creek.
Findings
A moderately diverse community of about 35 species of macroinvertebrates (19 in autumn and 28 in spring) was collected from the non-flowing channel, up to 14 metres wide and 60 centimetres deep in places, during autumn and spring 2014. The community was not dominated by any species but included low to moderate numbers of nematodes, leeches, introduced (Physiella) and native snails (Angrobia, Posticobia and Glyptophysa), water mites (Oxus), amphipods, beetles, biting midges, chironomids, waterbugs, damselflies, dragonflies and caddisflies. The presence of holes in the banks indicated that yabbies also occurred at the site. Most of the community comprised generalist and opportunistic species with a widespread distribution in the region and generally tolerant of moderately high salinity and poor water quality. The collection of a few waterbugs (Diaprecoris) was the only unusual record for this site because they normally inhabit wetland habitats rather than streams. No sensitive, rare or specialised macroinvertebrates were recorded and the only fish seen or collected at the site were a few threatened Southern Pygmy Perch (Nannoperca australis) during the spring survey.
The water was moderately fresh to saline (salinity ranged from 2,420-3,541 mg/L), well oxygenated (66-68% saturation), clear and slightly coloured, and with moderate to high concentrations of nutrients such as nitrogen (0.43-1.13 mg/L) and phosphorus (0.02-0.04 mg/L).
The sediments were dominated by detritus, silt, sand and filamentous algae; samples taken from below the surface were grey silts that released sulfide when tested in spring, indicating that the sediments were generally anaerobic or lacking in oxygen and a harsh environment for most burrowing species to live in. Fine silt deposits more than 10 centimetres deep were recorded from the middle of the channel in places. No significant areas of bank erosion were noted but cattle accessed and defaecated on the banks and in the channel during both sampling periods.
Moderate growths of phytoplankton were recorded (chlorophyll a ranged from 3.1-4.3 µg/L) and filamentous algae (Cladophora) covered more than 10% of the channel during the year. Over 65% of the creek was also covered by a range of submerged (Callitriche and Chara) and emergent plants (Phragmites, Schoenoplectus, Typha, Juncus, Isolepis and Mimulus). These plant responses highlight the effects from the regular nutrient enrichment of the stream from land-use sources in the catchment.
The 5-10 metre wide riparian zone was dominated by paperbark trees over sedges, rushes and introduced grasses. The surrounding vegetation at the site was paperbark woodland that was being grazed by cattle.
Special environmental features
Henry Creek remains a significant habitat for a threatened fish (Southern Pygmy Perch) and a diverse assemblage of macroinvertebrates and plants from the South East.
Pressures and management responses
Pressures
Management responses
Livestock grazing in the catchment (causing sediment erosion and adding excessive nutrients).
Limited riparian zone vegetation (reducing habitat quality, increasing sediment erosion).
The South East NRM Board assists landholders to access targeted grant opportunities for revegetation and ecosystem protection when funding is available. The Board also works closely with landholders consistent with the Board’s Regional Pest Management Plan to control weeds on their property and to assist in halting their spread to other properties.
Observed Condition
Expected Condition
