Kenton Creek near Gumeracha
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment and fine sediment.
- Diverse macroinvertebrate community dominated by species tolerant of pollution.
- Excessive growths of algae and aquatic plants.
- Flow patterns severely disrupted by human activity.
- Degraded riparian zone with limited native vegetation.
About the location
Kenton Creek is a small stream which rises about six kilometres south of Gumeracha in the southern Mount Lofty Ranges. It flows north through the town, discharging into the River Torrens about one kilometre downstream. Livestock grazing (34%) and horticulture (21%) are the main land uses in the upper catchment, with some dairying. Urban development covers another 18%.
The site selected for monitoring was located opposite the Gumeracha Effluent Ponds, downstream from the Adelaide to Mannum Road.
Adelaide and Mount Lofty Ranges NRM Regional Summary 2008
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 very high nutrient levels. Occasional inflows of stormwater from the Gumeracha township, the large number of farm dams in the upper catchment and a degraded riparian zone with limited vegetation to filter runoff were all likely to contribute towards the degradation of this stream.
The creek was a series of isolated, deep pools more than 10 metres wide in places when samples were taken in November 2008.
A diverse community of 43 macroinvertebrate species was collected, including 12 species of flies, eight beetles and six water bugs. The community was dominated by species tolerant of high nutrient levels and poor water quality such as snails, chironomids and worms. None of the more sensitive or rare species such as stoneflies and mayflies were found.
The water was fresh (salinity of 728 mg/L), moderately well oxygenated (59% saturation) and slightly cloudy, or turbid. It contained high levels of nutrients such as nitrogen (0.9 mg/L) and phosphorus (0.12 mg/L), and moderate amounts of small algae, or phytoplankton, which thrive in nutrient enriched water.
Large growths of green filamentous algae (Cladophora and Spirogyra) covered up to 35% of the creek surface, and large amounts of aquatic plants grew in the channel, including Cumbungi (Typha), spikerush(Eleocharis), watermilfoil (Myriophyllum), a fern (Azolla) and duckweed (Spirodela).
The sediments were mostly detritus, silt and decomposing algae; they were blackened and anaerobic, another indication of too much organic material and high nutrient levels entering the creek.
The riparian zone was limited, with only a narrow band of sparse River Red Gums and introduced grasses. A recreational park with scattered River Red Gums, planted shrubs and lawns covered the surrounding area.
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 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.|
|Large nutrient inputs from numerous diffuse sources in the catchment (leading to extensive growth of algae 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 working with industry and landholders to ensure efficient use of fertilisers and discuss ways to reduce runoff of nutrients into waterways.|
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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.