Nairne Creek is a small stream in the southern Mount Lofty Ranges that rises north of Nairne and flows only occasionally after winter rains. It runs through the town before turning south-east to join Dawesley Creek and eventually draining into Mount Barker Creek. Most of the surrounding land upstream is used for livestock grazing (47%) and horticulture (29%), with 15% of the catchment area covered by urban development.
The site selected for monitoring was located in the lower reaches of the creek, off Ironstone Range Road at Petwood, about 10 kilometres east of Mount Barker.
The creek was given a Fair rating at this site because the ecosystem showed moderate changes to animal and plant life, and some changes to the way the ecosystem functions. It was evident the creek receives considerable loads of excess nutrients and fine sediments during wet periods.
Findings
The creek was dry when inspected in November 2008, and likely to have lacked regular flows for some time given the amount of non-aquatic plants that were growing in the channel. The introduced herb Watercress (Rorippa nasturtium-aquaticum) was the only plant species found which prefers wet habitats. Most of the rocks and depressions in the channel were covered by a mat of dry green filamentous algae (probably Cladophora).
Sediments found in the creek were mostly grey silts and rocks which were slightly blackened on the underside, indicating the drying pools had been anaerobic and sulfidic at least part of the time.
River Red Gums grew sparsely along the creek, as well as lignum, Stiff Flat Sedge (Cyperus vaginatus), introduced grasses and weedy herbaceous species such as fennel, celery and daisies.
The riparian zone was as wide as 10 metres in some places, and the surrounding area was covered with eucalypt woodland growing over introduced grasses. The area had been replanted with gums and wattles as part of landcare work.
Special environmental features
None identified, although previous fish surveys in the catchment have detected a few threatened Mountain Galaxias from further upstream in 2004 (M. Hammer, Aquasave Consultants, 2009).
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 SA Murray–Darling Basin NRM Board acknowledges the significant impacts that livestock have on aquatic environments and seeks to provide free technical advice and incentives to land managers for fencing and other works as funding permits. Funding incentives are limited in value and extent and require land managers to volunteer to be involved.
Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).
The SA Murray–Darling Basin NRM Board recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.
Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity.
The SA Murray–Darling Basin NRM Board is working with the Department for Water and the community to develop a water allocation plan and licensing system which aim to balance social, economic and environmental needs for water. The objective for providing water to the environment is to maintain and/or restore self-sustaining water-dependent ecosystems which are resilient in times of drought.
Observed Condition
Expected Condition
