First Creek, Waterfall Gully
2011 Aquatic Ecosystem Condition Report
- Permanently wet, flowing, freshwater creek in autumn and spring 2011
- Moderately diverse macroinvertebrate community with several rare, sensitive and flow-dependent species
- Evidence of slight nutrient enrichment
- Riparian vegetation dominated by planted vegetation downstream from the waterfall.
About the location
First Creek is a small stream in the Southern Mount Lofty Ranges that rises on the western side of Mount Lofty and Crafers, and flows in a north-westerly direction where is becomes channelised, as it passes through the north-eastern suburbs, until it discharges into Torrens Lake near the Adelaide Zoo. The monitoring site was located downstream from the waterfall, near the kiosk at Waterfall Gully. The major land use in the 569 hectare catchment is conservation (Cleland Conservation Park), with smaller areas used for urban and rural residential living, roads, commercial activities and stock grazing.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance including signs of nutrient enrichment and degraded riparian vegetation but the stream still provides habitat for numerous rare and sensitive species of macroinvertebrates.
A moderately diverse community of at least 37 species of macroinvertebrates was collected from the flowing creek, 3.1-4.8 m wide and up to 48 cm deep, in autumn and spring 2011. The creek consisted of large areas of fast-flowing riffle habitats and smaller sections of still to slow-flowing pools in the reach below the waterfall. The community was dominated by generalists and species tolerant to poor water quality such as chironomids, worms and blackflies. It also included smaller numbers of limpets, mites, amphipods, springtails, beetles, dixids, biting midges, mayflies, waterbugs, pyralid caterpillars, odonates, stoneflies and caddisflies. Several rare and sensitive species were collected, including a blackfly (Austrosimulium furiosum), mayfly (Atalophlebia australasica), stonefly (Dinotoperla evansi), dragonflies (Austrogomphus and Hemigomphus gouldii) and caddisflies (Apsilochorema gisbum, Ulmerochorema membrum, Lingora and Triplectides similis). A range of species normally associated with flowing water were also collected, including a blackfly (Simulium ornatipes), chironomid (Rheotanytarsus), hydropsychid caddisfly (Cheumatopsyche sp. 2) and many of the above-listed rare and sensitive species. The only fish seen at the site were small galaxiid fish in spring.
The water was fresh (salinity ranged from 159-194 mg/L), well oxygenated (80-134% saturated), clear and slightly coloured, and with low concentrations of nutrients such as nitrogen (0.19-0.31 mg/L) and phosphorus (0.01-0.02 mg/L).
The sediments were dominated by cobble, boulder and detritus. Samples taken from below the surface were sandy grey in appearance and showed no evidence that the sediments were anaerobic or lacked oxygen. A deposit of fine silt, less than 1 cm deep covered the creekbed in places but no evidence of any significant areas of erosion was noted in 2011.
Over 10% of the channel was covered by filamentous algae (mostly Cladophora) in spring and more than 90% of the creek was covered by a range of aquatic plants in autumn (Cyperus, Hydrocotyle, Juncus, Persicaria, Typha, Phragmites and introduced mint). The narrow riparian zone consisted of lawn grasses, planted gums, bottlebrush, sedges and irises on banks that have been channelised and protected to prevent erosion. The surrounding vegetation near the creek comprised planted deciduous trees around the carpark but native eucalypt woodland dominated the upstream catchment in the conservation park.
Special environmental features
First Creek provides a permanently flowing, freshwater stream that supports a wide range of rare, sensitive and flow-dependent species. It is one of the most significant streams in the region due to the dominance of native vegetation in its' catchment, which indicates it represents one of the few, best condition, reference watercourses in the State. It is also characterised by very fresh water and very low nutrient concentrations, which separates it from the majority of other streams in South Australia.
Pressures and management responses
|Widespread introduced weeds in the riparian zone at the site and upstream (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.|
|Limited riparian zone vegetation at the creek and upstream (reducing habitat quality, increasing sediment erosion).||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 nutrient inputs to the creek from numerous diffuse sources (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.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.