Nepourie Creek, Nepourie Spring
2012 Aquatic Ecosystem Condition Report
- Discontinuous, slow-flowing pools with small riffles present in autumn but the channel was dry in spring 2012
- Moderately diverse macroinvertebrate community dominated by mayflies, with a rare beetle and flow-dependent species present when the spring holds water
- Water was moderately fresh, clear and low in nutrients despite showing obvious signs of enrichment due to extensive algal growths
- Riparian vegetation consisted of native trees and shrubs over a largely native understorey
About the location
Nepouie Creek is a small stream that rises around Mount McTaggart in the Vulkathunha-Gammon Ranges National Park and flows in an easterly direction across Munyallina Valley, where it disappears underground on the plains surrounding the north-western edge of Lake Frome. The major land uses in the 7,655 hectare catchment, upstream from the site sampled,are grazing natural vegetation (67%) and national park (33%), although pastoral grazing effectively ceased in the early 1970’s when the Arkaroola area was de-stocked and turned into a wildlife sanctuary. The monitoring site was located off a track from Arkaroola Road, about 11 km north-north-east from Balcanoona.
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, bank erosion and the presence of weeds on the banks but the stream still provided habitat for a range of aquatic macroinvertebrates and plants.
A moderately diverse community of at least 22 species of macroinvertebrates was collected from the slow-flowing spring, 5.8 m wide and up to 20 cm deep, in autumn; the spring was dry when it was revisited in November 2012. The community was dominated by large numbers of baetid mayflies (Cloeon), biting midges (Bezzia) and caenid mayflies (Tasmanocoenis tillyardi). It also included smaller numbers of beetles (Allodessus, Sternopriscus, Platynectes, Eretes, Macrogyrus, Hydraena and Berosus nutans), mosquitoes (Anopheles), soldierflies, chironomids (Procladius, Larsia and Tanytarsus), waterbugs (Microvelia, Agraptocorixa and Anisops), odonates (Ischnura, Hemianax and Hemicordulia) and caddisflies (Triplectides australis). A number of blackfly larvae (probably Simulium ornatipes) and chironomids were also seen from a small area of fast-flowing riffle that was too small to sample with a net. The lack of non-insect groups such as flatworms, snails, mites and crustaceans was unexpected given the range of habitat types present but may be an indication that the spring dries too frequently to support permanent pool-dwelling species. The dominance by the two sensitive and commonly occurring mayflies from the region highlights the significance of the site but most macroinvertebrates collected were generalists and tolerant species that are widely distributed throughout the north of the State. The major exceptions were the hydrophilid beetle B. nutans that has rarely been collected from the region in the past and two habitat specialists that live in flowing water habitats (e.g. dytiscid beetle Platynectes and the blackfly larvae). The only fish recorded from the site were larval and adult Flinders Ranges Purple-spotted Gudgeon, a threatened species that had been translocated to the catchment from nearby Weetootla Creek in an attempt to establish another population in the region; obviously the drying of the stream reach in spring meant that any resident fish would have perished.
The sediments were dominated by filamentous algae, with smaller amounts of bedrock, cobble, pebble, gravel, sand, silt and detritus also present; samples taken from below the surface were grey gravels and showed no evidence that the sediments were anaerobic, or lacking in oxygen. Some minor bank erosion was noted from the site and attributed to rabbits, kangaroos and emus accessing the stream, particularly during the spring inspection when the spring was dry.
Only a small amount of phytoplankton was recorded from the spring (chlorophyll a 0.7 Âµg/L) but a filamentous alga (Cladophora) covered over 35% of the site when it was wet. Two types of aquatic plants (sedge Cyperus gymnocaulos and water ribbons Triglochin) extended over less than 10% of the spring. Note that even though the concentrations of nutrients in the water were low when measured, the large growth of filamentous algae and presence of aquatic plants indicate that the spring is enriched with excessive amounts of nutrients, presumably sourced by feral and native animals regularly accessing the stream throughout the year. The riparian vegetation around the spring was dominated by River Red Gums, Native Oranges, paperbarks and acacias over native shrubs (Hakea), sedges and introduced weeds and grasses on the poorly vegetated banks (25-49% vegetative cover). The surrounding vegetation at the site was low native woodland dominated by acacias and gums.
Special environmental features
Nepouie Creek is a largely natural, autumn-winter flowing, ephemeral stream in the Northern Flinders Ranges that provided habitat for a translocated population of threatened native fish species. It may, however, dry too regularly to enable it to provide a long-term alternative habitat for native fish to survive in. The spring site sampled also supports two sensitive mayflies, a regionally rare species of beetle, two flow-dependent species when it flows, and a wide range of common insect groups from across the region.
Pressures and management responses
|Feral goats, donkeys and rabbits are exerting excessive grazing pressure on vegetation, causing erosion and adding excessive nutrients to the watercourse.||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.|