Riparian vegetation was extensive and consisted of mostly native plants
Area map
About the location
Callawonga Creek is a small stream in the Southern Mount Lofty Ranges that rises at an elevation of about 330 m near Parawa and flows southwards, before eventually discharging into the Southern Ocean at Callawonga Beach. The major land uses in the 1,689 hectare catchment were stock grazing (65%) and native vegetation (25%), with smaller areas used for plantation forestry, roads, cropping, rural housing and dams. The site was located upstream from Callawonga Creek Road, about 19 km west from Encounter Bay on the southern Fleurieu Peninsula.
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 due nutrient enrichment (ie presence of filamentous algae and high nitrogen concentration in spring) but the creek provides a significant habitat for a large number of rare, sensitive and flow-dependent species of macroinvertebrates.
Findings
A diverse community of at least 35 species of macroinvertebrates was collected from the creek (29 species in autumn and 23 in spring), 1.5-3.2 m wide and up to 22 cm deep, in autumn and spring 2013. The creek consisted of equal areas of slow to moderately fast-flowing pools and shallower, faster-flowing riffle habitats in autumn but was dominated by pools in spring. The community was dominated by moderate numbers of amphipods (Austrochiltonia) in autumn, and included lower numbers of flatworms, limpets, worms, mites, yabbies, beetles, biting midges, blackflies, chironomids, dixid flies, mayflies, waterbugs, stoneflies and caddisflies. Many of these were common generalist, opportunistic and tolerant species, particularly the non-insect groups, waterbugs, beetles and chironomids found at this site. However, a large number of rare, sensitive and/or flow-dependent species were also collected, including a blackfly (Austrosimulium furiosum), stoneflies (Illiesoperla mayi and Dinotoperla evansi), mayflies (Centroptilum elongatum, Offadens sp5, Tasmanophlebia, Atalophlebia australasica and Thraulophlebia inconspicua) and caddisflies (Lingora aurata, Triplectides similis, Taschorema evansi, Taschorema complex and Oxyethira columba). There were also additional mayflies (Cloeon and Tasmanocoenis tillyardi) and caddisflies (Notalina, Lectrides and Hellyethira) recorded but they are among the more tolerant members of these insect groups. The rich mayfly, caddisfly and stonefly diversity found in this stream is comparable to that recorded from only the small number of best condition streams located in the Southern Mt Lofty Ranges in the State.
The water was fresh (salinity ranged from 447-487 mg/L), well oxygenated (83-127% saturation), clear and slightly coloured, and with low to moderate phosphorus concentrations (0.03 mg/L) but generally high nitrogen concentrations (0.49-1.17 mg/L), particularly in spring.
The sediments were dominated by detritus, silt and sand in the pools and by detritus and gravel in the riffles. Samples taken from below the surface were mostly grey sands that released sulphide when tested in spring, indicating that the sediments were at least occasionally anaerobic or lacking in oxygen. There was also no sign of any significant bank erosion at the site, despite cattle accessing and defaecating on the banks and in the creek near the site sampled in spring.
Only a small amount of phytoplankton was recorded from the creek (chlorophyll a ranged from 0.9-2.6 μg/L) but a coarse filamentous alga (Cladophora) persistently covered nearly 10% of the channel during 2013. Over 10% of the channel was also covered by a wide diversity of aquatic plants, including introduced watercress (Rorippa) and swamp lily (Ottelia), and natives such as cumbungi (Typha), knotweed (Persicaria), streaked arrowgrass (Triglochin striatum), water buttons (Cotula), buttercups (Ranunculus), pennywort (Hydrocotyle), pondweed (Potamogeton) and muskgrass (Chara). The riparian zone extended over 40m in width in places and was dominated by native vegetation, including gums, wattles, tea-trees, sedges and herbaceous plants. The surrounding vegetation near the creek comprised dense native woodland on one bank and introduced grasses and the occasional gum tree on the other bank where cattle grazing was the major land use.
Special environmental features
Callawonga Creek provides a permanently flowing, freshwater stream on the Fleurieu Peninsula and supports a large number of rare, sensitive and flow-dependent species of macroinvertebrates and a rich range of aquatic plants. Similar to nearby First Creek at Tunkalilla, it is among the most ecologically significant streams in the region and State, due to the rich diversity of aquatic life that inhabit the many pools and riffles that occur throughout its’ catchment.
Pressures and management responses
Pressures
Management responses
Moderate to large nutrient inputs to the creek from numerous diffuse sources (leading to extensive growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes working with industry and landholders to ensure efficient use of fertilisers and discuss ways to reduce runoff of nutrients into waterways.
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.
Observed Condition
Expected Condition
