Mount Barker Creek, near Mount Barker
2018 Aquatic Ecosystem Condition Report
- Permanently flowing, freshwater stream in spring 2018
- Moderately diverse macroinvertebrate community dominated by generalists and tolerant species, and with a few sensitive species
- Obvious signs of nutrient enrichment
- Narrow and weedy riparian zone
About the location
Mount Barker Creek is a moderately sized stream in the southern Mount Lofty Ranges that rises east of Echunga, flows in an easterly direction through the township of Mount Barker, and eventually discharges into the Bremer River near Callington. The major land uses are sheep grazing and both urban and rural residential living. The monitoring site was located downstream of the Mount Barker wastewater treatment plant on Mount Barker Springs Road, about four kilometres east of Mount Barker.
The creek was given a fair rating because the site sampled showed evidence of moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of nutrient enrichment (eg moderately high nutrient concentrations, large growths of algae and aquatic plants, moderate chlorophyll concentrations) and the riparian zone was narrow and degraded by weeds. However, the site was notable by the presence of a few sensitive and flow dependent macroinvertebrate species.
A moderately diverse community of about 31 species of macroinvertebrates was collected from the flowing creek, 1-6 metres wide and 56 centimetres deep in spring 2018. Fast-flowing riffle and slow-flowing edge habitats each comprised 50% of the site. The community was dominated by large numbers of species that are tolerant to poor water quality, such as introduced snails (Potamopyrgus and Physa), amphipods (Austrochiltonia) and waterbugs (Micronecta). A wide range of other macroinvertebrates were collected in smaller numbers, including flatworms, worms, native snails (Glyptophysa), limpets (Ferrissia), pea-clams (Sphaeridae), mites, freshwater shrimp, yabbies, isopods, beetles, blackflies (Simulium ornatipes), chironomids, biting midges, mayflies, waterbugs and caddisflies. The only sensitive species collected included a leptophlebiid mayfly (Atalophlebia australis) and stonefly (Dinotoperla evansi). The only flow-dependent species noted were moderate numbers of blackfly larvae and a dytiscid beetle (Platynectes).
The water was fresh (salinity of 704 mg/L), well oxygenated (118% saturation), slightly turbid, and with moderately high concentrations of nutrients such as nitrogen (0.7 mg/L) and phosphorus (0.07 mg/L).
The sediments in the riffle habitats consisted of bedrock, boulders, cobbles, pebbles, silt and algae whereas the slow-flowing pools comprised cobbles, silt, boulder and detritus. The underside of rocks were slightly black, indicating that the sediments had been anaerobic in the past due to the presence of excessive amounts of organic matter. Less than 1 cm of fine silt covered the creekbed. A small area of bank erosion (less than 10 metres) was noted, presumably caused by a previous high flow event scouring the edge of the streams.
A moderate amount of phytoplankton was recorded in spring, when more than 10% of the channel was also covered by green filamentous algae (Cladophora). Emergent aquatic plants (Bolboschoenus, Rumex, Typha, Cyperus and Triglochin) covered over 65% of the stream. Collectively, these various plant responses indicate the stream is enriched with nutrients. The narrow riparian zone consisted mainly of introduced grasses, fennel and celery under the river gum trees that lined the channel. The surrounding vegetation was mostly scattered gums over introduced grasses with patches of planted Allocasuarina and fruit trees.
Special environmental features
This site was previously sampled in 2010 when it was assigned a Poor condition rating. At that time the creek provided habitat for at least two sensitive types of macroinvertebrates, the mayfly (Atalophlebia) and gripopterygid stoneflies but had a poorer water quality (nitrogen concentrations ranged from 3–11 mg/L and phosphorus concencentrations ranged from 0.17–0.2 mg/L). Despite this, the catchment provided refuge habitats for a threatened native fish called Mountain Galaxias (Galaxias olidus) which was previously collected from the creek in 2008–09 (M Hammer, Aquasave Consultants). In spring 2018, the aquatic fauna and flora appears to be similar despite improvements to the water chemistry from the measurements recorded.
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 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.|
|Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity.||The SA Murray–Darling Basin NRM Board is working with the Department for Water and the community to develop a water allocation plan and licensing system which aim to balance social, economic and environmental needs for water. The objective for providing water to the environment is to maintain and/or restore self-sustaining water-dependent ecosystems which are resilient in times of drought.|
|Wastewater discharges, adding excessive nutrients and organic matter (leading to algal growth and aquatic weeds).||
Mount Barker Community Wastewater Management System
The SA Murray–Darling Basin NRM Board works closely with local government and encourages the development of reclaimed water for more appropriate uses.
Plans are being developed by the District Council of Mount Barker to minimise the discharge from the Community Wastewater Management System by significantly increasing reuse opportunities through expanded agricultural and reserve irrigation and the annual supply of the vast majority of effluent to the Kanmantoo mine, minimising, with the aim to eliminate, discharges to Mount Barker Creek.