Meadows Creek, near Willunga
2008 Aquatic Ecosystem Condition Report
- Affected by nutrient enrichment, erosion and fine sediment.
- Macroinvertebrate community dominated by species tolerant of pollution.
- Excessive growths of algae and aquatic plants.
- Riparian zone and creekbanks damaged by livestock.
- Catchment provides habitat to rare and threatened fish species.
About the location
Meadows Creek is a moderately large stream in the southern Mount Lofty Ranges that rises to the north of Meadows and flows in a southerly direction, where it eventually discharges into the Finniss River. The major land uses are dairying, livestock grazing, vineyards, forestry plantations, conservation parks and rural living areas.
The site selected for monitoring was located off Brookman Road, about nine kilometres east of Willunga.
The creek was given a Fair rating at this site because the ecosystem showed evidence of moderate changes to animal and plant life, and some changes to the way the ecosystem functions. Evidence showed human activity was having a significant impact on the creek, causing erosion and nutrient enrichment, and increasing sediment loads.
The creek channel was about nine metres wide at the site, with large pools connected by narrow, flowing riffles when sampled in spring 2008.
A moderately diverse community of 32 macroinvertebrate species was collected. The community was dominated by species tolerant to high nutrient levels such as snails and small crustaceans called water scuds (Austrochiltonia australis). Two rarely collected mites (Pionidae and Oxidae) were found at this site.
The water was moderately fresh (salinity of 1,350 mg/L) and moderately well oxygenated (63% saturation). It was clear but slightly coloured, with low to moderate concentrations of nutrients such as nitrogen (0.58 mg/L) and phosphorus (0.01 mg/L). Drought conditions probably resulted in lower concentrations of nutrients than might be expected when runoff from more typical seasonal rains is likely to flush them into the stream from adjacent paddocks.
The creekbed was made up mostly of clay and detritus, with large deposits of silt in the deeper parts of the channel. The sediments were blackened and anaerobic in places, suggesting too much organic material had entered the creek in the past.
Two types of green filamentous algae (Cladophora and Spirogyra) were found on the bottom of the pools. Up to 35% of the channel was covered with introduced weeds such as Watercress (Rorippa nasturtium-aquaticum) and buttercups (Ranunculus), and native aquatic plants such as Narrow-leafed Cumbungi (Typha domingensis), spikerush (Eleocharis) and water ribbons (Triglochin).
Native gum trees grew along the creek’s banks and further afield, with small amounts of native shrubs and groundcover, Sea Rush (Juncus kraussii) and introduced pasture grasses. Cattle had trampled the banks and accessed the creek, disturbing the site and contributing to erosion and nutrient loads.
Special environmental features
Recent fish surveys in the catchment have confirmed the presence of at least two threatened native fish species (Mountain Galaxias and Southern Pygmy Perch) from the mid to lower reaches of the creek (M. Hammer, Aquasave Consultants, 2009).
Pressures and management responses
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||The SA Murray–Darling Basin NRM Board acknowledges the significant impacts that livestock have on aquatic environments and seeks to provide free technical advice and incentives to land managers for fencing and other works as funding permits. Funding incentives are limited in value and extent and require land managers to volunteer to be involved.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The SA Murray–Darling Basin NRM Board recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.|