Coongra Creek, Road crossing
2012 Aquatic Ecosystem Condition Report
- Ephemeral to semi-permanent, non-flowing waterhole when sampled in autumn 2012
- Diverse macroinvertebrate community with a few regionally rare and sensitive species collected
- Water was fresh, slightly turbid and enriched with nutrients
- Riparian vegetation consisted of native trees and shrubs but no aquatic plants were recorded
About the location
Coongra Creek is a small stream that rises east of Marla in the Far North of the State and flows in an easterly direction before discharging into Alberga River during very wet years. Further downstream, Alberga River merges with Hamilton and Stevenson creeks to form the Macumba River, which eventually discharges into the northern part of Lake Eyre North, also only during exceptionally wet years. The major land use in the catchment is cattle grazing. The monitoring site was located just upstream from the Oodnadatta Track, about 30 km north-east from Welbourn Hill and 70 km east from Marla.
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 caused by nutrient enrichment but the stream provides an important habitat for a rich diversity of aquatic macroinvertebrates.
A diverse community of at least 25 species of macroinvertebrates was collected from the non-flowing, isolated waterhole, 5.8 m wide and only 24 cm deep, in autumn 2012. The community was dominated by large numbers of waterbugs (Micronecta and Agraptocorixa parvipunctata) and included smaller numbers of dytiscid beetles (Necterosoma, Hyphydrus, Megaporus, Eretes and Allodessus), chironomids (Cladotanytarsus, Tanytarsus, Parachironomus, Dicrotendipes, Ablabesmyia and Procladius), baetid mayflies (Cloeon), mites (Eylais), snails (Glyptophysa concinna), gyrinid beetles (Dineutus australis), hydrophilid beetles (Berosus nutans), crustaceans (Conchostraca), waterbugs (Anisops stali), dragonflies (Hemicordulia tau and Orthetrum caledonicum) and caddisflies (Triplectides australis). The mayfly and gyrinid beetle were the only regionally rare or sensitive macroinvertebrates collected but the community also included a mite and snail that have poor survival strategies to survive prolonged periods of drying. The other species are all insect groups, capable of aerially dispersing to other wetted habitats. The nymph of the dragonfly Hemicordulia tau is a large animal that takes many months to years to mature into an adult, so it is likely that this stream reach holds water in most years but may occasionally dry for at least part of the year. A moderate number of zooplankton was recorded from the site, including copepods, ostracods and a few cladocerans. No fish were recorded from the site when it was visited in May 2012.
The sediments were dominated by cobble, pebble and sand, with smaller amounts of gravel, silt, detritus and algae also present; samples taken from below the surface were grey clays and silts but showed no evidence that the sediments were anaerobic, or lacking in oxygen. Some past flood damage caused bank erosion over about 10% of the site. Cattle and kangaroos had accessed the banks of the stream and defaecated throughout the site, including on the edges of the channel and banks.
A small amount of phytoplankton was present (chlorophyll a 3.2 Âµg/L) but no blue-green algae or cyanobacteria were detected from the creek. About 10% of the shallow margins of the waterhole were covered by at least two types of filamentous algae (Cladophora and Spirogyra) but no aquatic plants were seen. The riparian vegetation was dominated by gum trees and sheoaks on the poorly vegetated banks (25-49% vegetative cover). The surrounding vegetation at the site comprised scattered native woodland and grasses.
Special environmental features
Coongra Creek provides habitat for many species of aquatic macroinvertebrates but probably dries too regularly to support aquatic plants or native fish at the site sampled.
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 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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- Cockayne, B., Schmarr, D., Duguid, A. & R. Mathwin (2013). “Lake Eyre Basin Rivers Assessment (LEBRA) 2012 Monitoring Report.” Report to LEBRA Oversight Group.