Cooper Creek, Minkie Waterhole
2012 Aquatic Ecosystem Condition Report
- Permanently wet, non-flowing, creek site when sampled in spring 2012
- Moderately diverse macroinvertebrate community with at least one sensitive species present
- Water was very fresh, turbid and enriched with nutrients
- Riparian vegetation consisted of native trees and shrubs, and the edges of the waterhole included a native aquatic plant and an introduced grass
About the location
Cooper Creek is a large stream in the Far North that rises at an altitude of 230m in western Queensland and flows south-westerly for over 1,500 km through increasingly arid woodland, grassland and desert before discharging into Lake Eyre. In the ‘channel country’ of the middle reaches it forms both deep, narrow channels which transport sand and mud at moderate flows and a large network of braided channels that transport clay-rich mud during high flow periods. As the river passes into South Australia it forms the one channel near Innamincka and then further downstream it extends across a wide floodplain and forms another mosaic of shallow freshwater and saline lakes, deep permanent and semi-permanent channel reaches, flooded woodlands and grasslands, samphire-lined claypans and other wetlands (for more details see Walker et al. 1997 and Silcock 2009). Flow patterns in the unregulated Cooper Creek are highly variable and driven by monsoonal summer rainfall in the upper catchment area in Queensland. Most water is retained or evaporates in the channel country and only 30% of overbank flows reaches Innamincka. As a result, Lake Eyre only receives water during extremely large floods.
The major land uses in the 296,000 square kilometre catchment are sheep and cattle grazing on native grasslands, with smaller areas used for rural towns and settlements, mining, tourism and national parks.
The monitoring site was located off the 15 Mile Track on Cooper Creek, about 10 kilometres west from Innamincka.
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 including nutrient enrichment and weeds dominating the understorey vegetation on the banks but the stream still provided habitat for a sensitive mayfly and a range of other aquatic macroinvertebrates. Note that the high nutrient concentrations recorded from the waterhole were similar to other sites sampled from Cooper Creek and were assumed to have originated from upstream grazing and cropping practices. Similarly, the high turbidity was sourced by floods naturally mobilising clays from the channel country in Queensland and was not obviously exacerbated by local land use practices.
A moderately diverse community of at least 13 species of macroinvertebrates was collected from the 70 m wide, non-flowing, arid-zone waterhole in spring 2012. The community was dominated by moderate numbers of mites and freshwater prawns (Macrobrachium) and included low numbers of 7 species of beetles, 2 waterbugs, a genus of baetid mayfly (Cloeon) and a chironomid (Cladotanytarsus). The prawn and chironomid are often associated with stream environments whereas the other groups are mostly tolerant, generalist species that frequent pool habitats. No rare or flow dependent species were recorded but the mayfly represents a sensitive species with a widespread distribution from the more permanent freshwater habitats in the eastern Lake Eyre Basin. The site sampled was notable due to the absence of snails, odonates and more species of flies, groups that commonly occur at other locations on Cooper Creek. A single carp gudgeon (Hypseleotris) was the only native fish caught at the site in 2012.
The water was fresh (salinity of about 128 mg/L), well oxygenated (103% saturated) and turbid (secchi depth 8 cm), with high concentrations of nutrients such as nitrogen (3 mg/L) and phosphorus (0.53 mg/L).
The sediments were dominated by detritus, with smaller amounts of clay, silt and sand also present; samples taken from below the surface were grey clays and silts and showed no sign that the sediments had recently been anaerobic, or lacking in oxygen. No evidence of any significant bank erosion was noted during the site visit.
A large amount of phytoplankton was present (chlorophyll a 11 Âµg/L) which included a small amount of cyanobacteria or blue-green algae (chlorophyll b 1.4 Âµg/L). No filamentous alga was observed at the waterhole but over 10% of the edge was covered by a native plant called Water Primrose (Ludwigia peploides) and introduced couch grass. The riparian vegetation was dominated by gum trees over lignum and acacias, with couch grass growing in the understorey in patches; between 50-79% of the banks were vegetated. The surrounding vegetation at the site was low gum and acacia woodland over lignum shrubs.
Special environmental features
Cooper Creek in the vicinity of Minkie Waterhole provides an important permanent refuge habitat for a moderately diverse range of aquatic macroinvertebrates from the region and at least one species of native fish inhabits the site.
Pressures and management responses
|High nutrient concentrations causing excessive algal growth although the source(s) of the nutrients are not known.||The EPA in collaboration with the Department for Environment, Water and Natural Resources is anticipating a study program to investigate the source(s) of nitrogen and phosphorus. This will provide a better understanding of nutrient dynamics with the aim of developing a management strategy (if appropriate).|
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- Silcock, J. (2009). “Identification of Permanent Refuge Waterbodies in the Cooper Creek and Georgina-Diamantina River Catchments for Queensland and South Australia.” Final report to South Australia Arid Lands Natural Resource Management Board.\
- Walker, K.F., Puckridge, J.T. & S.J. Blanch (1997). Irrigation development on Cooper Creek, central Australia – prospects for a regulated economy in a boom-and-bust ecology. Aquatic Conservation: Marine and Freshwater Ecosystems Volume 7, pages 63-73.