Kersbrook Creek rises among the hills east of Kersbrook and flows south into the northeast corner of Millbrook Reservoir in the southern Mount Lofty Ranges. Livestock grazing (43%) is the main land use in the catchment, but there are also extensive areas of protected native vegetation (31%).
The site selected for monitoring was located in the lower reaches of the creek, upstream from Bagshaw Road, more than three kilometres south of Kersbrook.
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. Evidence confirmed very high nutrient levels, and a disturbed and limited riparian zone.
Findings
The creek was a series of still pools, up to 60 centimetres deep, when the site was sampled in November 2008.
A richly diverse community of 43 macroinvertebrate species was collected, including 19 species of flies, six beetles and six mites. Species tolerant of high organic enrichment accounted for 57% of the community, including chironomids (Corynoneura and Chironomus) and snails (Glyptophysa). There was a lack of more sensitive types such as mayflies, stoneflies and caddisflies. Odonates such as dragonflies and damselflies were also surprisingly absent, despite the presence of suitable habitat.
The water was moderately fresh (salinity of 1,429 mg/L), moderately well oxygenated (56% saturation), and slightly cloudy, or turbid. It contained moderate to high levels of nutrients such as nitrogen (0.94 mg/L) and phosphorus (0.03 mg/L).
A large amount of phytoplankton was found suspended in the water despite more than 65% of the creek being shaded by surrounding vegetation, and growths of green filamentous algae (Cladophora) were found on the water’s surface. Small patches of aquatic plants grew in the channel, including Cumbungi (Typha), Swamp Crassula (Crassula helmsii), introduced loosestrife (Lythrum), starwort (Callitriche) and stonewort (Chara).
Detritus and fine particles of sand, silt and clay formed the creekbed; the sediments were blackened and anaerobic, indicating too much organic material had entered the stream in the past.
The riparian zone was narrow, with a band of River Red Gums and introduced willow trees growing over a wide range of introduced grasses and weeds. The surrounding area was mainly covered with eucalypt woodland and pasture grasses.
Special environmental features
None identified.
Pressures and management responses
Pressures
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.
Observed Condition
Expected Condition
