Tatiara Creek, west from Bordertown
2014 Aquatic Ecosystem Condition Report
- Isolated pool habitats in autumn but dry in spring 2014
- Sparse macroinvertebrate community with no rare or sensitive species when it holds water at this site
- Obvious signs of gross nutrient enrichment
- Riparian vegetation limited to a few gum trees over introduced grasses
- Large silt and clay deposits in the channel
About the location
Tatiara Creek is a moderately sized stream in the upper South East with a catchment area over 430 square kilometres. It rises in western Victoria in the Lillimur area and flows in a westerly direction through Bordertown and Poocher Swamp before disappearing underground via karst “runaway holes” several kilometres west from Bordertown. The major land uses are grazing and cropping, and the stream receives urban stormwater as it traverses through Bordertown. The monitoring site was located downstream from the wastewater treatment plant between Pigeon Flat Road and Meat Works Road, about one kilometre west from Bordertown.
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 nutrient enrichment, fine sediment deposited in the channel and poor riparian habitat. The site has remained in essentially the same condition since it was last assessed in 2009.
A sparse community of about 9 species of macroinvertebrates was collected from isolated pools, 8 metres wide and over 44 centimetres deep, in autumn 2014; the creek was dry in spring. The community was dominated by tolerant chironomids (Chironomus) and waterbugs (Micronecta), and included smaller numbers of native (Isidorella) and introduced (Physiella) snails, worms, dytiscid beetles and mosquitoes (Anopheles). No sensitive or rare species were found but the site supported a small number of regionally uncommon planorbid snails (Isidorella).
The water in autumn was fresh (salinity of 151 mg/L), moderately well oxygenated (54% saturation), slightly turbid, and with high concentrations of nutrients such as nitrogen (1.58 mg/L) and phosphorus (0.3 mg/L).
The sediments were dominated by clay, detritus, sand and silt, with smaller amounts of gravel also present; samples taken from below the surface were grey silts and clays that showed no evidence to indicate they had recently been anaerobic or lacking in oxygen. No evidence of any significant bank erosion was noted despite the presence of cow droppings on the banks and in the channel of the creek. A large deposit of more than 10 centimetres of fine silt was recorded from the middle of the channel, indicating that significant bank erosion had probably occurred further upstream and been transported to the Bordertown area during past flooding events.
A large growth of phytoplankton (chlorophyll a 29 Âµg/L) was recorded from the pools at the site but no filamentous algae or other types of aquatic plants were seen during 2014; the lack of macrophytes is probably an indicator of the highly ephemeral nature of the creek at the site sampled.
The narrow (<5 metres wide) riparian zone consisted of a few gum trees over introduced grasses and bare ground. The surrounding vegetation consisted of largely cleared cattle grazing grassland with a few scattered gum trees present in the local landscape.
Special environmental features
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 South East NRM Board supports targeted projects that provide opportunities for landholders to access grants for fencing for stock exclusion from time to time for priority catchments.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The South East NRM Board assists landholders to access targeted grant opportunities for revegetation and ecosystem protection when funding is available. The Board also works closely with landholders consistent with the Board’s Regional Pest Management Plan to control weeds on their property and to assist in halting their spread to other properties.|