Waterfall Creek, near Ingallala Falls
2012 Aquatic Ecosystem Condition Report
Permanently wet freshwater creek which was flowing in spring 2011 and autumn 2012
Diverse macroinvertebrate community with many rare and sensitive species
Emerging signs of nutrient enrichment
Riparian vegetation mostly invaded by weeds
About the location
Waterfall Creek is a small stream that rises near Parawa and flows north-east where it joins the Yankalilla River before discharging to the sea at Normanville. The major land uses in this 1,042 hectare catchment are grazing pastures (44%), softwood production (33%) and native vegetation (15%). The monitoring site was located just downstream of the Ingallala Falls, which is upstream from Hay Flat Road.
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 emerging signs of nutrient enrichment and weedy riparian zones but the stream provides habitat for several rare and sensitive species of macroinvertebrates.
A diverse community of at least 69 species of macroinvertebrates was collected from this flowing creek, 3.2 m wide and up to 30 cm deep in spring 2011 and autumn 2012. The community was dominated by amphipods (scuds) in the pool habitat and the non-biting midge Cricotopus and small unidentified stoneflies in the fast-flowing habitat. Other species collected in small numbers included round worms, hydrobiid snails, freshwater limpets, segmented worms, six types of mites, marsh beetles, four species of biting midge, moth fly larvae and dance fly larvae, at least 18 species of non-biting midge, a common species of mayfly, waterbugs and a dragonfly. Many sensitive and rare species, as well as flow-dependent species, were also collected from this site, including fly larvae from the family Thaumaleidae, blackfly larvae (Austrosimulium and Simulium), mayflies (Atalophlebia and Thraulophlebia), stoneflies (Dinotoperla, Illiesoperla and Austrocerca), and caddisflies (Taschorema, Ulmerochorema, Lingora, and Triplectides similis). Introduced brown trout was also present in the creek and native fish called Climbing Galaxias (Galaxias brevipinnis) has been collected from this creek in the past. Other rare and sensitive species have been collected from Waterfall Creek in the past, just downstream of this site, and include a mayfly (Centroptilum), a dragonfly (Austrogomphus), three different species of riffle beetles (Simsonia, Kingolus and Coxelmis) and a caddisfly (Orphninotrichia).
The water was fresh (salinity ranged from 342-440 mg/L), well oxygenated (95-99% saturation) and clear, with high concentrations of nutrients such as nitrogen (0.9-2.19 mg/L) and phosphorus (0.08-0.31 mg/L).
The sediments were dominated by cobbles and pebbles in the flowing sections and silt and detritus in the non-flowing areas. Samples taken from below the surface were brown silts and clay and were sulphidic, or lacking in oxygen; probably due to the decomposition of the organically enriched sediments. Only small deposits of silt covered the streambed to a depth of about 1 cm in places and no significant areas of bank erosion were seen.
A moderate amount of phytoplankton (chlorophyll a ranged from 3.53-8.37 µg/L) and small amounts of blue-green algae (chlorophyll b ranged from 0.16-0.3 µg/L) were recorded but no filamentous algae was seen. About 35% of the site was covered by aquatic plants including Carex, Isolepis, Polygonum, Phragmites, Rorrippa, Rumex, Gahnia, and Arum Lillies. Bracken, Phragmites, eucalypts and acacias and along with blue periwinkle, lillies and other weeds grew along the banks. The surrounding vegetation was predominately native with gums trees, acacias and an understorey of bracken and weeds such as blue periwinkle. Pine forests surrounded the creek in the local area.
Special environmental values
Waterfall Creek provides important habitat for a wide range of rare, sensitive, flow-dependent and more generalist aquatic macroinvertebrates from the region. It also supports a threatened fish species which adds to the environment importance of this stream in the Mount Lofty Ranges.
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