Mount Barker Creek, near Mount Barker
2010 Aquatic Ecosystem Condition Report
- Permanently flowing, freshwater stream in autumn and spring.
- Moderately diverse macroinvertebrate community with a few rare and sensitive species.
- Obvious signs of gross nutrient enrichment.
- Riparian vegetation mostly comprised introduced grasses and weeds.
About the location
Mount Barker Creek is a moderate 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 Poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance, including very high nutrient loads due to discharges from the wastewater treatment plant, fine sediment deposition and a lack of native vegetative cover in the riparian zone.
A moderately diverse community of about 34 species of macroinvertebrates was collected from the flowing creek, 3–7 metres wide and 55 centimetres deep, in autumn and spring 2010. Fast-flowing riffle habitats were present during both seasons and comprised 50% of the site in spring. The community was dominated by large numbers of species that are tolerant to poor water quality and high nutrient levels, such as amphipods (Austrochiltonia australis) in the non-flowing habitats and blackfly larvae (Simulium ornatipes), stoneflies and worms in the riffles.
A wide range of other macroinvertebrates was also collected in smaller numbers, including snails (native species and introduced Physa and Potamopyrgus), mites, freshwater shrimps, yabbies, springtails, beetles, craneflies, soldierflies, chironomids, mayflies, waterbugs, odonates and caddisflies. The only sensitive species collected were a leptophlebiid mayfly (Atalophlebia australis) and a small, unidentified species of stonefly (Family Gripopterygidae). The list of species recorded also included an uncommonly collected chironomid (Eukiefferiella) and the two most tolerant mayflies found in the State (Cloeon and Tasmanocoenis). The only fish collected was the introduced mosquitofish (Gambusia).
The water was fresh to moderately fresh (salinity of 425 mg/L in autumn and 1,115 mg/L in spring), generally well oxygenated (51–90% saturation), slightly turbid and coloured, and with very high concentrations of nutrients such as nitrogen (3.03–11.2 mg/L) and phosphorus (0.17–0.2 mg/L).
The sediments in the riffle habitats consisted of bedrock, boulders, cobbles, pebbles and algae whereas the slow-flowing and still pools were mostly comprised bedrock, silt and detritus. Samples taken from below the surface were black in autumn, indicating that too much organic material had entered the creek in the past. Subsequent sampling during the higher flow period in spring showed no evidence of the sediments being black or anaerobic. A deposit of 1–5 centimetres of silt covered the creekbed in the non-flowing areas of the site. A small area of bank erosion (less than 10 metres), associated with a bank collapse near the road bridge, was recorded in spring.
A large amount of phytoplankton was recorded in spring, when more than 35% of the site was also covered by green filamentous algae (Cladophora). Emergent aquatic plants (Bolboschoenus, Rumex, Typha, Cyperus, Isolepis and Triglochin) covered over 10% of the stream in both autumn and spring.
The riparian zone consisted mainly of introduced grasses, onion weed, bracken and cumbungi (Typha), with a few sheoaks (Casuarina) and gum trees also present. The surrounding vegetation was mostly urban gardens, with areas of grazed paddocks further downstream.
Special environmental features
Mount Barker Creek provides habitat for at least two sensitive types of macroinvertebrates, the mayfly (Atalophlebia) and gripopterygid stoneflies. They are organic feeding detritivores that are frequently found in fast-flowing, freshwater streams in the Mount Lofty Ranges. The creek also provides refuge habitats for a threatened native fish called Mountain Galaxias (Galaxias olidus) that was collected from the creek during 2008–09 (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 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.