Spoehr Creek, near Balhannah
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment.
- Moderately diverse macroinvertebrate community dominated by species tolerant of pollution.
- Excessive growths of algae and aquatic plants.
- Extensive streambank erosion and limited native vegetation.
About the location
Spoehr Creek rises to the north of Verdun in the southern Mount Lofty Ranges. The small stream flows through protected areas of native vegetation (29%), and agricultural land used mainly for livestock grazing (37%) and horticulture (14%), before reaching the Onkaparinga River about one kilometre southwest of Balhannah.
The site selected for monitoring was located off Spoehr Road, near the junction of the two waterways.
The creek was given a Poor rating at this site because the ecosystem showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystem functions, due to high nutrient levels and poor habitat.
Small areas of very shallow, flowing riffles connected large pools to form the creek at this site in Spring 2008.
A moderately diverse community of 37 macroinvertebrate species was found along the edges of the pools. The community was dominated by moderate numbers of the tiny crustacean, water scud (Austrochiltonia australis) and introduced snails (Physa). Species tolerant of high nutrient levels were the most common, with very low numbers of the more sensitive species. The introduced Mosquitofish (Gambusia) was the only fish species detected, occurring in large schools throughout the stream.
The water was fresh (salinity of 760 mg/L), well oxygenated (127% saturation), and clear with a slight colour. There were moderate to high concentrations of nutrients such as nitrogen (0.76 mg/L) and phosphorus (0.07 mg/L) in the water.
While there were only moderate amounts of phytoplankton, dense growths of green filamentous algae covered up to 65% of the bottom of the pools. Throughout the channel, large growths of aquatic plants such as Water Ribbons (Triglochin), watermilfoil (Myriophyllum) and Swamp Crassula (Crassula helmsii) provided additional evidence of the consequences of high nutrient loads.
The creekbed was mostly detritus, algae and silt, with smaller areas of bedrock, gravel and sands. The sediments were blackened and anaerobic, providing habitat suited only to the most tolerant species.
The creekbanks had been extensively eroded and damaged by livestock. Large areas of introduced grasses covered the riparian zone, with patches of River Red Gums and other planted gums. Cereal crops occurred across most of the surrounding landscape.
Special environmental features
The creek provides habitat for one species of mayfly (Atalophlebia australis) that usually occurs in small, well shaded, flowing streams in the Adelaide Hills.
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.