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 from nutrient enrichment. The creek provides significant habitat for a large number of rare, sensitive and flow-dependent species of macroinvertebrates.
Findings
A diverse community of at least 51 species of macroinvertebrates was collected from the creek (31 species in autumn and 36 in spring), 2.7 m wide and up to 65 cm deep, in autumn and spring 2016. The creek consisted of slow to moderately fast-flowing pools and shallower, faster flowing riffle habitats. The community was dominated by large numbers of amphipods (Austrochiltonia) and low to moderate numbers of hydrobiid snails, including the introduced Potamopyrgus, worms, mites, yabbies, springtails, beetles, crane flies, 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, Newmanoperla thoreyi, Dinotoperla evansi and Austrocerca tasmanica), mayflies (Centroptilum elongatum, Tasmanophlebia, Atalophlebia australasica, Nousia fuscula and Thraulophlebia inconspicua) and caddisflies (Lingora aurata, Triplectides similis, Taschorema evansi). 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. An introduced trout seen in spring was the only fish recorded from the site.
The water was fresh (salinity ranged from 235-421 mg/L), well oxygenated (77-78% saturation), clear and slightly coloured, and with low to moderate phosphorus concentrations (0.03-0.05 mg/L) but generally high nitrogen concentrations (0.78-1.16 mg/L). Some froth was present at the site in autumn.
The sediments were dominated by detritus and sand in the pools and by cobble, pebble and gravel in the riffles. Samples taken from below the surface were mostly grey clay and silts that released sulfide 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.
Only a small amount of phytoplankton was recorded from the creek (chlorophyll a ranged from 0.88-1.03 μg/L) but no filamentous algae was noticed during either sampling season. Over 35% of the channel was covered by a wide diversity of aquatic plants, including both submerged plants (Aponogeton and Triglochin) and emergent plants (Typha, Persicaria, Cotula, Ranunculus, Hydrocotyle, Cyperus, Juncus, Isolepis and the introduced Rumex). The riparian zone was dominated by native vegetation, including gums and sedges and the surrounding vegetation comprised dense native woodland.
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
Nutrient inputs to the creek from numerous diffuse sources (potentially leading to excess growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board 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.
Insufficient natural water flows in the creek resulting from water extraction and climate variability
Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.
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.
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Observed Condition
Expected Condition
