Riparian vegetation consists of native trees with sedges and weeds with dense woodland beyond
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 including emerging signs of nutrient enrichment and sediment deposition but the stream provides habitat for several rare and sensitive species of macroinvertebrates.
Findings
A highly diverse community of at least 50 species of macroinvertebrates was collected from this flowing creek, approximately 3.4 m wide and 60 cm deep, in autumn and spring 2015. The creek consisted of slow-flowing pools with fast-flowing riffle sections between the pools in both autumn and spring 2015. The site was dominated by mites, amphipods, non-biting midge larvae, mayflies and caddisfly larvae from the families Hydrobiosidae and Leptoceridae. Other species collected in smaller numbers included a range of generalist and pollution tolerant species, such as worms, snails, seven different families of fly larvae, mayflies, waterbugs, stoneflies, and caddisflies. Some sensitive and rare species, as well as flow-dependent species, were also collected, including the riffle beetle Simsonia, blackfly larvae (Austrosimulium), mayflies (Centroptilum, Offadens, Atalophlebia, Nousia and Thraulophlebia), stoneflies (Dinotoperla, Illiesoperla, Newmanoperla, Riekoperla and Austrocerca), and the caddisflies Apsilochorema, Taschorema, Lingora and Triplectides similis. Introduced fauna such as trout and the snails Potamopyrgus and Physiella were seen in the creek. Small galaxiid fish and yabbies were also seen.
The water was fresh (salinity ranged from 345-449 mg/L), well oxygenated (81-114% saturation) and clear but slightly coloured, with moderately high concentrations of nutrients such as nitrogen (0.79-0.97 mg/L) and phosphorus (0.03-0.05 mg/L). Some froth was seen on the surface of the water in autumn.
The sediments in the riffle sections were dominated by cobbles and pebbles with some silt also present. In the pools fine sediment and detritus dominated. Samples taken from below the surface were grey clay with some silt present and showed evidence of being anaerobic, or lacking oxygen during some months of the year. Small deposits of silt covered the streambed to a depth of about 5 cm in places and some areas of bank erosion (<10%) were also seen, likely due to cattle accessing the site and trampling the banks. Cattle droppings were also evident on the banks.
A small amount of phytoplankton (chlorophyll a ranged from 0.24-1.18 µg/L) and small amounts of the filamentous algae Spirogyra (<10%) were seen in spring. More than 35% of site was covered by a range of aquatic plants, including the emergent plants (Callitriche, Potamogeton, Aponogeton, Cotula, Cyperus, Hydrocotyle, Isolepis, Polygonum, Ranunculus, Rorrippa, Rumex and Triglochin. The riparian zone consisted of acacias, gums, sedges and weeds. The surrounding vegetation was dense woodland.
Special environmental features
Callawonga Creek provides important habitat for many species sensitive to pollution and dependent on the near permanent flows that occur in this creek such as the riffle beetle, the mayflies Centroptilum, Offadens, Atalophlebia, Nousia and Thraulophlebia, the stoneflies Dinotoperla, Illiesoperla, Newmanoperla, Riekoperla and Austrocerca and the caddisflies Apsilochorema, Taschorema, Lingora and Triplectides similis.
Pressures and management responses
Pressures
Management responses
Livestock having direct access at the site and upstream (causing sediment erosion and adding excessive nutrients).
The Adelaide and Mount Lofty Ranges NRM Board's land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.
Widespread introduced weeds in the riparian zone at the site and upstream (reducing habitat quality).
The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.
Insufficient natural water flows in the creek resulting from water extraction and climate variability (reducing ecological integrity).
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.