Cooper Creek, Embarka Waterhole
2012 Aquatic Ecosystem Condition Report
- Permanently wet, non-flowing, creek site when sampled in spring 2012
- Sparse macroinvertebrate community with one rare species collected
- Water was very fresh, enriched with nutrients and only slightly turbid compared to other sites from the catchment
- Riparian vegetation consisted of native trees and shrubs, and the edges of the waterhole were covered by a native aquatic plant
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 (Qld only) 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 in the Innamincka Regional Reserve near Gidgealpa off Walkers Crossing Track, about 55 km 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. Therewas evidence of human disturbance including nutrient enrichment and stock accessing the site but the waterhole still provided habitat for a moderately diverse macroinvertebrate community. 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.
A sparse community of at least 8 species of macroinvertebrates was collected from the 100 m wide, non-flowing, arid-zone waterhole in spring 2012. The community was dominated by large numbers of baetid mayflies (Cloeon) and included smaller numbers of 4 species of waterbugs, and a species of freshwater prawn (Macrobrachium), thiarid snail and caddisfly (Triplectides australis). The community included groups normally associated with stream environments (prawn and snail) and others that are typically found in pool habitats and temporary waters throughout the Far North region (insects such as beetles, bugs, mayflies and caddisflies). The thiarid snail (Thiara) was the only rarely collected macroinvertebrate recorded from the site and the large number of baetid mayflies was also an unusual record for the region for this sensitive group of insects. The waterhole was notable due to the absence of groups commonly found elsewhere along Cooper Creek, including beetles, flies, odonates and mites. A few carp gudgeon (Hypseleotris) were collected from the site but no introduced fish or aquatic invertebrates were recorded in spring 2012.
The water was fresh (salinity of about 202 mg/L), well oxygenated (155% saturated) and only slightly coloured and turbid (secchi depth 65 cm), with high concentrations of nutrients such as nitrogen (2.05 mg/L) and phosphorus (0.237 mg/L).
The sediments were dominated by living and dead detritus, with smaller amounts of clay, sand, silt and algae; samples taken from below the surface were grey clays and silts and showed no evidence that they were anaerobic, or lacking in oxygen. No evidence of any significant bank erosion was noted but cattle faeces were noted on the banks surrounding the waterhole.
A small amount of phytoplankton was present (chlorophyll a 2.8 Âµg/L) and nearly 10% of the shallow edge of the waterhole was covered by filamentous algae (Spirogyra). Over 35% of the waterhole was covered by a native aquatic plant called water milfoil (Myriophyllum). The riparian vegetation was dominated by lignum, gum trees and acacias on the well vegetated banks (50-79% vegetative cover). The surrounding vegetation comprised low gum and acacia woodland and a rural house was located within 200 m of the site.
Special environmental features
Cooper Creek at Embarka Waterhole provided habitat for only a few species of aquatic macroinvertebrates, a submerged aquatic plant and at least one species of native fish. A freshwater turtle was also seen at the site. Consequently, the waterhole provides habitat for a range of aquatic species in the region.
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).|
|Livestock have direct access at the site and upstream in the catchment exerting excessive grazing pressure on vegetation, causing sediment erosion and adding some nutrients to the watercourse.||The SA Arid Lands Natural Resources Management Board recognizes 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.|
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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.