Eleven sites were sampled from the region during autumn and spring 2012. They were located from Wild Dog Creek near Murray Town in the south to Willow Creek near Hawker in the north. Land use was dominated by agriculture (stock grazing and cereal cropping) on the flatter land, with grazing of remnant native vegetation and conservation areas confined to the steeper ranges around the Melrose to Wilmington area (including Mount Remarkable National Park) and Mount Plantagenet to the east from Hawker.
Sites monitored in the Northern and Yorke region during 2012 were considered to be in a Very Good to Poor condition. No sites were assigned to either the Excellent or Very Poor classes and given the scale of vegetation clearance and nutrient enrichment evident in 2012, it is unlikely that any stream in the region remains unaffected by human activities. Of the sites assessed, one site (9%) was in a Very Good condition with little change to animal and plant life; 3 sites (28%) were considered to be Good condition with only minor changes to animal and plant life; 5 sites (45%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; and 2 sites (18%) were in Poor condition with evidence of major changes in animal and plant life, and moderate changes to the way the ecosystems functioned.
The better sites were located in well vegetated catchments to the east from Hawker (Willow Creek) and near Melrose in Mount Remarkable National Park (Mount Remarkable Creek), or were permanently wet sites that sustained a wide range of freshwater species throughout the year (Kanyaka Creek and Pekina Creek downstream from the reservoir). These sites were characterised by good riparian habitats dominated by natural vegetation that included a range of coarse and fine sediments, and showed little to no bank erosion caused by stock accessing the banks or streambed during the year. The wet sites showed some evidence of nutrient enrichment but were not obviously overwhelmed by some of the problems often associated with eutrophication.
The sites assigned to the Fair ratings showed significant evidence of nutrient enrichment (e.g. high nutrient concentrations, large growths of algae and/or aquatic plants, anaerobic sediments, dominance by plant and detrital feeding macroinvertebrates, and/or the extent of catchment land use modifications for the dry sites). They included two dry sites that maintained sufficient riparian buffer vegetation to provide at least some in-stream protection from adjacent land uses (Beautiful Valley Creek and Wirreanda Creek), two saline sites from Willochra Creek that sustained a saline-tolerant aquatic community (sites from Particoona and Castle Springs) and Spring Creek which only held water in autumn and supported a wide range of tolerant and some regionally important species.
The worst sites that were assigned Poor ratings were from largely cleared, agricultural catchments with highly degraded riparian habitats along two ephemeral streams (Wild Dog Creek and Pekina Creek upstream from the reservoir); neither held water in 2012 and both lacked any of the appropriate physical and biological features that could lead to a better rating when water persists for long enough to support aquatic communities during wetter periods.
The aquatic macroinvertebrate communities of the water-holding streams were dominated by very tolerant, generalist species that occasionally included low numbers of a few rare and sensitive species. The waterbugs (Micronecta, Agraptocorixa and Anisops), amphipod crustacean (Austrochiltonia) and baetid mayfly (Cloeon) were usually the most abundantly collected macroinvertebrates, along with chironomids (including Procladius, Chironomus, Dicrotendipes and Larsia), mites (Koenikea and Arrenurus) and dytiscid beetles (Necterosoma). The non-flowing pool habitats also supported low numbers of yabbies, beetles, mosquitoes, biting midges, dragonflies and leptocerid caddisflies, whereas the only flowing riffle, at Kanyaka Creek, provided habitat for several flow-dependent species (e.g. blackfly Simulium ornatipes, hydropyschid caddisfly Cheumatopsyche and dytiscid beetle Platynectes).
The most diverse stream was Kanyaka Creek which was also the only stream that provided alternating flowing riffle and still pool habitats. The diversity of habitats meant that this fresh to slightly saline stream provided an important refuge for many generalist species, as well as the two widely distributed but sensitive mayflies (Cloeon and Tasmanocoenis tillyardi) and the more tolerant flow-dependent species found in the north of South Australia. Any reduction in the extent and duration of flow would threaten the habitat requirements for many of the species found in this stream and invariably lead to a worse condition rating being assigned in the future. Water quality effects such as increasing salinity, higher nutrient concentrations, excessive algal and plant growths, and blackened water from low oxygen levels could all contribute to the degradation of any stream where flow patterns are reduced due to extractions or the placement of in-stream barriers.
The only other significant wet site sampled was Spring Creek which rises off the eastern side of Mount Remarkable National Park and flows into Willochra Creek near Wilmington. This creek had freshwater pools present in autumn and supported a regionally rare and sensitive leptophlebiid mayfly (Thraulophlebia inconspicua) that has a restricted distribution in the Flinders Ranges to streams in the Mount Remarkable area. Several other rare, sensitive and uncommon species were also collected from this site including baetid mayflies, a beetle (Hydrochus) and two molluscs (Ferrissia and Angrobia).
The only fish recorded from the region included introduced mosquitofish (Gambusia) and native Lake Eyre Hardyhead (Craterocephalus eyresii) from the two Willochra Creek sites. Most streams sampled in 2012 were too ephemeral to provide suitable habitat for fish to persist in the landscape, however, a wider diversity of fish species are known to occur further south in the Broughton and Wakefield River catchments.
Most streams in the region had limited riparian habitats with, at best, a single line of River Red Gums lining the banks over introduced grasses, weeds and patches of sedges or rushes.
Few rare or sensitive species of macroinvertebrates were found in the region in 2012 but the most notable were the widespread presence of the baetid mayfly (Cloeon) from the fresher streams and the presence of the leptophlebiid mayfly (Thraulophlebia inconspicua) from Spring Creek. A number of molluscs, mites, beetles and caddisflies have also only been occasionally collected from the region in the past but there is limited information on their distribution and life history needs to confirm their regional significance in these assessments at this stage.
The presence of flowing riffle habitats and flow-dependent species at Kanyaka Creek is also notable due to the lack of similar habitat at other sites in the region in 2012.
The only native species of fish recorded during 2012 was the Lake Eyre Hardyhead (Craterocephalus eyresii) which co-occurred with an introduced pest (Mosquitofish) at the two most saline sites sampled on Willochra Creek. The hardyhead is commonly found from streams in the Lake Eyre Basin, so its presence in part of the Lake Torrens Basin suggests some fish obviously moved between basins during a wetter period in the past.
