Neales Creek, Stewart Waterhole
2012 Aquatic Ecosystem Condition Report
- Permanently wet, non-flowing, waterhole when sampled in autumn 2012
- Moderately diverse macroinvertebrate community with no rare or sensitive species
- Water was fresh, slightly turbid and enriched with nutrients
- Riparian vegetation consisted of native trees and shrubs and no aquatic plants were detected
About the location
Neales Creek is a medium sized stream in the Far North of the State that rises about 15 km south-east from Welbourn Hill as two main branches that flow in an easterly direction, before merging into the one channel north from Oodnadatta and eventually discharging into the western margins of Lake Eyre North during very wet years. The major land use in the catchment is cattle grazing. The monitoring site was located off a track from the Mount Barry HS to Oodnadatta Road, about 17 km south from Oodnadatta.
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 and minor bank erosion caused by cattle accessing the waterhole but the stream provides habitat for mussels, yabbies and various types of commonly occurring aquatic insects.
A moderately diverse community of at least 13 species of macroinvertebrates was collected from the non-flowing waterhole, 15 m wide and over 1 m deep, in autumn 2012. The community was dominated by large numbers of waterbugs (Micronecta gracilis) and chironomids (Cladotanytarsus, Tanytarsus, Cryptochironomus and Parachironomus), and included smaller numbers of caddisflies (Triplectides australis and Oecetis), dytiscid beetles (Antiporus and Allodessus), a waterbug (Agraptocorixa parvipunctata) and coenagrionid damselflies. All are very tolerant, generalist insect species, capable of aerially dispersing throughout the arid stream network in the north of the State. No rare or sensitive species were collected and the lack of snails, mites, mayflies, long-lived dragonfly nymphs or any flow-dependent species indicates that the site probably dries in some years. However, the presence of yabby holes around the margins of the waterhole also indicates that the site remains wet in most years, since this species is capable of surviving in wet burrows for at least several months of the year. Similarly, empty mussel shells were seen at the site which supports the contention that the waterhole is regularly wet because while mussels may favour permanent waters, they can survive occasional drying periods by burrowing into the wet sediments below the bed of the waterhole. Large numbers of zooplankton were also noted from the site, including cladocerans and copepods that were commonly recorded from other waterholes in the region. No fish were seen at the site.
The water was fresh (salinity of 353 mg/L), only moderately well oxygenated (43% saturation), slightly coloured and turbid, and with high concentrations of nutrients such as nitrogen (1.5 mg/L) and phosphorus (0.11 mg/L).
The sediments were dominated by clay and detritus, with smaller amounts of sand and silt also present; samples taken from below the surface were grey clays and silts and showed no evidence that the sediments were anaerobic, or lacking in oxygen. Bank erosion was present over about 10 m of the site due to cattle accessing and damaging the waterhole.
A moderate to large growth of phytoplankton was present (chlorophyll a 10.2 Âµg/L) which included a small amount of blue-green algae or cyanobacteria (chlorophyll b 1.23 Âµg/L). Less than 10% of the shallow margins of the waterhole were covered by filamentous algae but no aquatic plants were recorded from the site. The riparian vegetation was dominated by gum trees and acacias on the poorly vegetated banks (25-49% vegetative cover). The surrounding vegetation at the site comprised low chenopod shrubland.
Special environmental features
Stewart Waterhole on Neales Creek was sampled for fish in May 2012 as part of the Lake Eyre Basin Rivers Assessment, when 4 native species were collected (Bony Bream, Desert Rainbowfish, Barred Grunter and Spangled Perch)(Cockayne et al. 2013). Consequently, the waterhole provides habitat for several species of native fish and a moderately diverse range of aquatic macroinvertebrates.
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.|