Hadrian Creek, near Cherry Gardens
2008 Aquatic Ecosystem Condition Report
- Affected by nutrient enrichment and fine sediments.
- Diverse macroinvertebrate community dominated by species tolerant of pollution.
- Riparian zone dominated by exotic trees and weeds.
- Creek provides important habitat for several notable species.
About the location
Hadrian Creek is a small waterway that rises in the Scott Creek Conservation Park south of Stirling in the Mount Lofty Ranges, and flows west to join Scott Creek about two kilometres south of Cherry Gardens. Almost half the catchment is covered with protected areas of native vegetation; most of the remainder is used for grazing livestock.
The monitoring site was located off Scott Creek Road, just upstream from where the creek enters the larger Scott Creek.
The river was given a Fair rating at this site because the ecosystem had moderate changes to animal and plant life, and some changes to the way the ecosystem functions. Multiple lines of evidence confirmed excess nutrients were affecting its biological condition.
At the time of sampling in December 2008, the stream was only three to four metres wide and consisted of shallow pools connected by smaller areas of flowing riffles.
The pools provided habitat for a diverse community of 51 species of macroinvertebrates, covering every major group expected from a cool-water stream in the Mount Lofty Ranges, apart from stoneflies. Snails and chironomids tolerant to high nutrient levels dominated the community. The only species collected that were sensitive to poor water quality were single individuals of a mayfly from the family Leptophlebiidae and a fly larva from the family Dixidae.
The water was fresh (salinity of 700 mg/L) and moderately well oxygenated (60% saturation). It was also slightly cloudy, or turbid, and contained moderate to high concentrations of nutrients such as nitrogen (0.8 mg/L) and phosphorus (0.08 mg/L).
Sediments on the creek bed were mostly made up of detritus, silt, clay and cobbles; samples collected from beneath the surface were blackened and anaerobic, which is an indicator that too much organic matter had entered the creek. The banks of the stream were heavily eroded by slumping caused by high flows after periods of heavy rain.
Green filamentous algae (Cladophora) covered up to 65% of the bottom of the stream. Small patches of emergent aquatic plants occurred along the edge of the creek, including species of a rush (Juncus) and sedge (Isolepis), and introduced Watercress (Rorippa nasturtium-aquaticum), Cape Pond Lily (Aponogeton distachyos) and mint (Mentha).
The riparian zone was dominated by introduced plants such as deciduous quince trees, blackberries and pasture grasses. The surrounding area was covered by stringy bark eucalypts, native hopbushes, and introduced varieties of dog roses and pasture grasses.
Special environmental features
The creek provides habitat to several notable native species, including a mayfly (Koorrnonga inconspicua), fly larva from the family Dixidae, at least five types of caddisflies (Hellyethira, Hydroptila, Lectrides, Oecetis and Triplectides) and small, shrimp-like crustaceans from the rarely collected Perthiidae family.
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.|
|Extensive weed growth in the riparian zone at the site and upstream (causing habitat disturbance).||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.|
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.