Warburton Creek, Cowarie Crossing Waterhole
2012 Aquatic Ecosystem Condition Report
- Semi-permanent, isolated waterhole when sampled in spring 2012
- Moderately diverse macroinvertebrate community with possibly 1 rare species and at least 2 species of native fish present
- Water was saline, clear and enriched with nutrients
- Riparian vegetation consisted of native trees and shrubs and two aquatic plants were recorded from the waterhole
About the location
Warburton Creek forms downstream from the confluence of the Diamantina and Georgina rivers in Goyder Lagoon, in the north of South Australia, and flows in a south-westerly direction for about 150 km before discharging into Lake Eyre. Both inflowing rivers rise in central west Queensland and flow south-west for about 900 km through central Queensland and the ‘channel country’ before merging into the one well-defined channel downstream from Goyder Lagoon.
Flow patterns in the unregulated Warburton and upstream catchments are highly variable and driven by monsoonal summer rainfall in the upper catchment area of Queensland. The Diamantina River, along with Cooper Creek, are among the most variable major rivers in the world, characterised by ‘boom’ (major floods) and ‘bust’ (major dry periods and drought) climatic cycles. In extremely wet years when rainfall reaches around 500 mm year across much of the upstream catchments, water flows down the Warburton River and reaches as far downstream as Lake Eyre. Large stretches of the Diamantina and Georgina rivers have little reliable water but a small number of widely-spaced permanent and semi-permanent freshwater waterholes occur throughout each river system. Most waterholes on Warburton Creek, in contrast, tend to go saline within 6-12 months of filling but a few waterholes such as Yelpawaralinna, Cowarie, Anarowidinna and Emu Bone Waterholes hold freshwater for many months following flooding flows (for more details see Silcock 2009 – under the Further Information heading).
The major land use along Warburton Creek is cattle grazing.
The monitoring site was located about 10 km north from Cowarie on a track off the Cowarie-Mungeranie Track, about 250 km north of Marree in northern South Australia.
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 including nutrient enrichment, stock accessing the banks and weedy riparian zones but the stream provides habitat for a wide range of aquatic species.
A moderately diverse community of at least 17 species of macroinvertebrates was collected from the 9 m wide, non-flowing, isolated arid-zone waterhole in spring 2012. The community was dominated by large numbers of waterbugs (Micronecta robusta and Micronecta gracilis) but included smaller numbers of 5 types of chironomids (Coelopynia, Polypedilum, Parachironomus, Cladotanytarsus and Procladius), 2 waterbugs (Anisops thienemanni and Microvelia), 2 damselflies (Austroagrion watsoni and Ischnura), 2 biting midges (Nilobezzia and Culicoides), 2 caddisflies (Triplectides australis and Ecnomus) a freshwater prawn (Macrobrachium australiense) and a beetle (Sternopriscus maedfooti).The assemblage was dominated by tolerant insect groups such as waterbugs and chironomids that are commonly found in other waterholes in the region. The only regionally rare macroinvertebrates recorded were a chironomid (Coelopynia) and an uncommonly collected caddisfly (Ecnomus). Small hardyheads and gobies were the only native fish caught from the site; they were too small to be accurately identified.
The water was saline (salinity of about 7,850 mg/L), well oxygenated (118% saturated) and clear but slightly coloured, with only moderate to high concentrations of nutrients such as nitrogen (0.75 mg/L) and phosphorus (0.07 mg/L).
The sediments were dominated by silt and sand, with smaller amounts of detritus, boulder, clay, bedrock and cobble; samples taken from below the surface were sulfidic grey clays and silts, indicating that the sediments were anaerobic, or lacking in oxygen. Some small areas of bank erosion caused by wind and past flood damage were evident in places, and some deposits of cattle faeces highlighted that stock visit the waterhole on occasions.
A large amount of phytoplankton was present (chlorophyll a 24.3 Âµg/L) and included some blue-green algae or cyanobacteria (chlorophyll b 1.2 Âµg/L). No filamentous alga was seen but 2 types of aquatic macrophytes (sedge Cyperus and Water Buttons Cotula) extended over about 10% of the margins of the waterhole. The riparian vegetation was dominated by acacias, lignum, cypress pines and gums over a few weed species on the moderately vegetated banks (50-79% vegetative cover). The surrounding vegetation on nearby sand dunes comprised scattered gum trees over weeds and grasses.
Special environmental features
Warburton Creek at Cowarie Crossing Waterhole provides some habitat for at least one type of waterbird, Purple Swamphen, which frequent well-vegetated wetland habitats with permanent water. The waterhole also supports at least two native species of fish found in the Diamantina catchment.
Pressures and management responses
|Livestock have direct access at the site and upstream in the catchment exerting excessive grazing pressure on vegetation, causing sediment erosion and adding excessive nutrients to the watercourse.||The SA Arid Lands Natural Resources Management Boardrecognizes that both direct and diffuse impacts on aquatic ecosystem condition can occur through direct stock access and excessive grazing pressure from stock and feral herbivores. Technical advice and incentives are offered to land managers in the region, as funding permits, to address these impacts through appropriate activities suitable for the context. In addition, projects are underway across the region to identify, prioritise and address impacts at key aquatic sites.|
|Excessive weed growth in the riparian zone||The SA Arid Lands Natural Resources Management Board provides technical advice and incentives for the management of introduced weeds and feral pest animals, as funding permits. Pest management efforts are guided by a region-wide strategy, based on risk assessment, to determine priority locations and species. Funding is actively sought from a number of sources to support region-wide integrated management.|