Adelaide and Mount Lofty Ranges NRM Regional Summary
2008 Aquatic Ecosystem Condition Report
A total of 40 sites were sampled across the region in spring 2008, including six sites on the Fleurieu Peninsula, and 34 sites in the southern Mount Lofty Ranges and on the Adelaide Plains.
- Most streams affected by nutrient enrichment
- Cool, wet, well-vegetated streams with permanent or near permanent flow providing habitat for many rare and sensitive species
- Agriculture and urban development affecting water quality, plant and animal life in many streams
- Riparian zones degraded, with limited trees and understoreys invaded by weeds
- Allowing livestock to graze creekbanks a widespread practice in the region
Every site showed evidence of nutrient enrichment to varying degrees, and significant disturbance to the riparian vegetation. Runoff carrying nutrients and sediment from cropping and grazing land was found to be a significant issue affecting water quality in agricultural catchments. The streams with the best condition ratings were all located in the wetter parts of the region where flowing habitats were still present, ranging from well developed riffle habitats to smaller areas of slowly flowing water connecting pool habitats. The poorest sites were significantly affected by point source discharges or urban stormwater, mostly in the mid to lowland reaches of small creeks with extensively modified banks and vegetation. Across the region, invasions of exotic grasses and weeds had almost totally replaced native understorey plants in the riparian zones of every stream sampled.
Five sites in the higher rainfall areas of the Mount Lofty Ranges were assigned a good rating because their ecosystems showed evidence of relatively minor changes to their animal and plant life, although there were early signs of nutrient enrichment and some disturbance to understorey vegetation. These streams included Jupiter Creek at Echunga, Echunga Creek near the Mount Bold Reservoir, Aldgate Creek at Aldgate, Brownhill Creek at Mitcham and Deep Creek at Norton Summit.
Sixteen sites in the region were assigned a fair rating because their ecosystems showed moderate changes to animal and plant life, and some changes to the way the ecosystems functioned. Every stream sampled from the Fleurieu Peninsula was given this rating, including Congeratinga, Yankalilla, Dog Trap and Waitpinga creeks and two sites along the Inman River (off Inman Valley Rd, near Victor Harbor and off Victor Harbor Bypass, Victor Harbor). There were several indicators of high nutrient concentrations entering the creeks directly from a wastewater treatment plant (Inman River) and more diffusely from agricultural practices in the catchment, which often involved allowing cattle to have direct access to the creekbeds and banks. The other sites occurred in the Mount Lofty Ranges from largely agricultural landscapes (e.g. Malcolm, Victoria, Tenafeate, Fourth, Chambers, Hadrian and Yettie creeks, and the Torrens and Onkaparinga rivers) or from mixed land uses with a wastewater treatment plant in the upper reaches (e.g. Sturt River).
The remaining sites occurred in either well cleared agricultural country or urban streams and rated much poorer depending on the level of nutrient enrichment and disturbances to the vegetation, flow, habitat and water quality.
Thirteen sites were assigned a poor rating because their ecosystems showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystems functioned. They included streams adversely affected by urban development such as Dry, Kenton, Panalatinga and Pedler creeks and the South Para River in Gawler. Streams from agricultural catchments that were also assigned a poor rating included Cox, Jacob, Kersbrook, Spoehr and Tanunda creeks and a site on the lower Gawler River at Virginia Park. Another site at Hahndorf Creek was affected by the discharge from a wastewater treatment plant, urban stormwater and agricultural land uses in the upper catchment, and Millbrook Creek was affected by Millbrook dam and agricultural development further upstream.
Six sites were assigned the lowest rating of a very poor condition because their ecosystems showed evidence of major changes to both the animal and plant life, and a significant breakdown in the way the ecosystems functioned because of human disturbance in their catchments. They included Inverbrackie Creek near Woodside that was significantly degraded by stock accessing the banks and Heathfield Creek at Heathfield that received the concentrated discharge of treated effluent from a wastewater treatment plant. The adverse effects from urban stormwater were a major issue at four sites on the Adelaide Plains at Gawler, Burton, Wynn Vale and Salisbury East. Stormwater was disrupting flows, depositing pollutants and sediment, and causing erosion to the mostly dry stream channels of Gawler and Little Para rivers, and Dry and Cobbler creeks.
Special environmental features
Sampling at a range of sites in the region since 1994 has identified a number of streams in the region that support rare and sensitive species of macroinvertebrates.
Sampling in Spring 2008 confirmed Brownhill, Fourth, Echunga, Deep, Aldgate and Cox creeks, and the Sturt River were continuing to provide refuge for several sensitive and rare species that prefer cool, wet climates. All these streams were typically well shaded and had flowing water present, which provided habitat for a wide diversity of aquatic species to colonise and use. Significant species collected included stoneflies (Riekoperla naso and Austrocerca tasmanica), mayflies (Atalophlebia, Koorrnonga inconspicua and Nousia fuscula) and caddisflies (Taschorema and Ulmerochorema membrum).
Streams in this region are also known to provide habitat for a number of other regionally rare species such as the riffle beetle (Simsonia leai), chironomid (Aphroteniella tenuicornis), baetid mayfly (Centroptilum elongatum) and various caddisflies (e.g. Orphninotrichia maculata, Atriplectides dubius, Apsilochorema gisbum, Tasimia, Orthotrichia bishopi, Oxyethira columba and Lingora). First and Sixth creeks, which both flow into the Torrens River, are particularly significant streams in the Mount Lofty Ranges because they provide refuge habitats for a wide diversity of rare and sensitive species of macroinvertebrates and several native fish species as well.
Pressures and management responses
|Insufficient natural water flows in some creeks resulting from water extraction and climate variability (ie drought) (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.|
|Widespread introduced trees and weeds in riparian zones (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.|
|Livestock having direct access in some creeks (causing sediment erosion and adding excessive nutrients).||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 some creeks (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.|
|Stormwater runoff containing high nutrient and sediment loads discharging to some creeks (causing habitat disturbance, algal growth and aquatic weeds).||The Adelaide and Mount Lofty Ranges NRM Board has a well developed stormwater quality improvement, harvesting and reuse program which has installed (and maintains) gross pollutant (and silt) traps in several watercourses across the region to catch litter, debris and silt in order to minimise impacts and damage to seagrass in the receiving marine environment. Stormwater captured is also treated through artificial wetlands across the region which act as suspended solid and nutrient filters; these wetlands also provide important habitat for many native species.|
|Large nutrient inputs to some creeks 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.|
|Saline groundwater inflows to some creeks (reducing ecological integrity).||The Adelaide and Mount Lofty Ranges NRM Board has installed telemetered groundwater monitoring stations at key locations within the region. These are monitored for level and salinity; unusual results (such as high salinity influxes) are investigated.|
|Failing onsite wastewater treatment systems in some catchments, adding nutrients through shallow subsurface flows or overland flows to creeks (leading to algal growth).||Failing onsite wastewater treatment systems in the Mount Lofty Ranges Watershed are being addressed by improving maintenance of existing systems, upgrading to a more effective system, or via connection to a local government Community Wastewater Management Systems or to an SA Water sewer network, where these are available. The Mount Lofty Ranges Waste Control Program is addressing failing onsite systems by identifying and facilitating upgrades. This effective program is being delivered by the Adelaide Hills Council in partnership with the AMLR NRM Board, SA Water, Department of Health and the EPA.|
|Wastewater discharges to some creeks, adding excessive nutrients and organic matter (leading to algal growth and aquatic weeds).||
SA Water Wastewater Treatment Plants at Hahndorf and Heathfield
SA Water assess and undertake scheduled process improvement actions at wastewater treatment plants, with the aim to reduce environmental risk and ensure operations are compliant with EPA licence conditions.
This aquatic ecosystem condition summary report is based on monitoring data collected by the EPA and prepared in conjunction with the Adelaide and Mount Lofty Ranges NRM Board