Echunga Creek, near Mount Bold Reservoir
2008 Aquatic Ecosystem Condition Report
- Initial signs of nutrient enrichment starting to degrade the creek.
- Diverse macroinvertebrate community.
- Important habitat for rare and sensitive insect and fish species that are not often found together.
- Mix of native plants and weeds in the creek and on the banks.
About the location
Echunga Creek is a network of small streams in the Onkaparinga catchment of the Mount Lofty Ranges. It rises in the township of Echunga and flows in a southwesterly direction into Mount Bold Reservoir. Livestock grazing is the major agricultural land use in the area (44%), together with dairying (10%) and forestry (10%). Urban development (13%) and protected areas of native vegetation (14%) are also significant. Farm dams are common on all the major streams that feed into Echunga Creek. The monitoring site was located four kilometres off Razor Back Road, near Mount Bold Reservoir.
The creek was given a good rating at this site because the ecosystem showed evidence of relatively minor changes to its animal and plant life. However, there were some clear, emerging signs of occasional high nutrient loads degrading the creek, which could lead to further decline.
At the time of sampling in November 2008, the stream was only two metres wide and consisted of shallow, isolated pools.
A diverse community of 51 macroinvertebrate species was found. The community was dominated by organic feeders tolerant to high nutrient levels and poor water quality, such as the tiny crustacean, water scud (Austrochiltonia australis), chironomids and worms. There were also a number of rare and sensitive species of mites, mayflies, caddisflies and one species of stonefly. A number of fish were also observed, including introduced redfin and native species such as the threatened Mountain Galaxias (Galaxias olidus) and possibly the more widely distributed Flathead Gudgeon (Philypnodon grandiceps).
The water was fresh (salinity of 670 mg/L), well oxygenated (68% saturation) and clear, with low concentrations of nutrients such as nitrogen (0.3 mg/L) and phosphorus (0.02 mg/L). However, it is likely runoff after heavy rains in winter would carry significant loads of nutrients and sediments into this stream and generate higher nutrient concentrations.
Only a small amount of phytoplankton was found in the water, however up to 35% of the site was covered with green filamentous algae (Cladophora).
The sediments were mostly detritus, cobbles and fine silt. Samples collected from below the surface were blackened and anaerobic, or lacking in oxygen, which is an indication that too much organic material had entered the water.
Several herbaceous varieties of aquatic plants were found in the creek, including buttercups (Ranunculus), Swamp Crassula (Crassula helmsii), marsh-flower (Villarsia), sedge (Isolepis), introduced Arrowhead (Sagittaria graminea) and plantain (Plantago), as well as a number of submerged plants such as stonewort (Chara), watermilfoil (Myriophyllum) and Water Ribbons (Triglochin). Emergent plants such as Narrow-leafed Cumbungi (Typha domingensis), rushes (Juncus) and Stiff-Flat Sedge (Cyperus vaginatus) were also found growing in and along the creek.
Stringybark gums, acacias, woody weeds such as broom, and introduced grasses dominated the riparian zone and surrounding vegetation.
Special environmental features
The creek provides habitat for a wide range of sensitive species, rarely found together in the Mount Lofty Ranges, including mites from the Oxidae, Hygrobatidae, Unionicolidae and Pionidae families, a mayfly (Nousia fuscula), stonefly (Austrocerca tasmanica) and threatened native fish (Mountain Galaxias).
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 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.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||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 revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion.|
|Large decrease in natural water flows (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 and prepared in conjunction with the Adelaide and Mount Lofty Ranges NRM Board.