Adelaide and Mount Lofty Ranges NRM Regional Summary
2011 Aquatic Ecosystem Condition Report
Seventy two sites were sampled from the region during autumn and spring 2011. They were located from the Light River catchment in the north to the Inman River on the Fleurieu Peninsula in the south. Land use was dominated by agriculture (stock grazing and cereal cropping) and residential living, with patches of remnant native vegetation largely confined to the wetter, steeper hills, gullies, along creeklines and as part of roadside vegetation.
- 15% of sites were assigned to the Very Good or Good condition ratings whereas the remaining 85% of sites were Fair, Poor or Very Poor; no sites were assessed to be in Excellent condition
- The better streams lie in the wetter catchments with large areas of remnant native vegetation and only low to moderate damage caused by stock grazing
- The most significant streams in the region include First, The Deep and Yankalilla creeks from the Fleurieu Peninsula, and parts of the Onkaparinga River and First, Sixth and Brownhill creeks from the Adelaide Hills; all show some evidence of nutrient enrichment
- An introduced crayfish (Marron) and Brown and Rainbow Trout have been released into some of the best waters in the region and threaten to seriously degrade the biology of each affected stream
- All other streams show evidence of significant nutrient enrichment, smothering by fine sediment deposition, degraded riparian habitats and/or the presence of pest plants and fish
- Streams in the Mid North have been salinised due to widespread vegetation clearance and are characterised by salt tolerant species and degraded riparian habitats
- Macroinvertebrate communities were dominated by generalists and tolerant species with most rare and sensitive species only found from freshwater streams with permanent to near permanent flow
- Riparian habitats typically comprise a line of River Red Gums or weedy tree species over introduced grasses and weeds
- Improvements in land management practices need to be widely implemented to reduce the movement of nutrients and fine sediment into streams throughout the region
Sites monitored in the Adelaide and Mount Lofty Ranges region during 2011 were considered to be in a Very Good to Very Poor condition. No sites were assigned to the Excellent condition class and given the scale of vegetation clearance and nutrient enrichment evident in 2011, it is unlikely that any stream in the region remains unaffected by human activities. Of the sites assessed, one site (1.4%) was in a Very Good condition with little change to animal and plant life; 10 sites (13.9%) were considered to be Good condition with only minor changes to animal and plant life; 27 sites (37.5%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; 24 sites (33.3%) were in Poor condition with evidence of major changes in animal and plant life, and moderate changes to the way the ecosystems functioned; and 10 sites (13.9%) were Very Poor with evidence of major changes in animal and plant life, and the way the ecosystems functioned.
The better sites were located in high rainfall catchments from the Fleurieu Peninsula (e.g. First Creek, The Deep Creek and Yankalilla River) and Southern Mount Lofty Ranges (e.g. Workanda and First creeks, Northern branch of Brownhill Creek, two sites on Sixth Creek (near Castambul and near Montacute Heights), Tributary of Kersbrook Creek, and one site from both the Onkaparinga and South Para rivers). These sites were characterised by moderately diverse to diverse macroinvertebrate communities with at least several rare, sensitive and flow-dependent species, well vegetated riparian zones, and evidence of low to moderate levels of nutrient enrichment.
In contrast, the worst sites were from largely cleared catchments with degraded riparian habitats and included ephemeral streams (Tributary streams of Gomersal, Congeratinga, Blackfellows and Stockwell creeks, Unnamed creek to Myponga Beach, Adams and Pine creeks) and wet streams with degraded macroinvertebrate communities and poor water quality (e.g. Tributary of Waitpinga, Little Para River and Walkers Creek).
The sites assigned to either the Fair or Poor ratings showed significant evidence of nutrient enrichment (e.g. high nutrient concentrations, large growths of algae and/or aquatic plants, anaerobic sediments) but were distinguished by the number of rare and sensitive species and extent of damage to the riparian zone. The Fair sites tended to occur in streams with more extensive riparian habitats and some remnant native vegetation in their catchments and included many of the larger streams in the Adelaide Hills. The Poor sites included streams receiving wastewater discharges, significant runoff from agricultural land uses, and Mid North waterways that have been salinised due to extensive land-clearance that occurred after the region was settled in the late 1800’s.
The aquatic macroinvertebrate communities of most streams were typically dominated by a small number of very tolerant species and included low numbers of rare and sensitive species. The amphipod crustacean (Austrochiltonia) was usually the most abundantly collected macroinvertebrate along with chironomids (including Cricotopus, Chironomus, Dicrotendipes and Polypedilum). Where flowing water was present, large numbers of blackfly larvae (mostly Simulium ornatipes) were often recorded whereas the slow to non-flowing pools usually provided habitat for many waterbugs (Micronecta and Microvelia), worms, introduced snails (Physa and Potamopyrgus) and baetid mayflies (Cloeon). Low numbers of a range of caddisflies, dragonflies and damselflies were also found at most sites.
Streams that flow provided more habitat complexity and supported a wider range of aquatic species than those that ceased to flow or dried up for at least part of the year. A range of rare and sensitive species that frequent flowing riffle habitats were collected from the better sites, including stoneflies, mayflies, caddisflies, beetles and various types of flies. These sites also tend to support the state-listed threatened fish called Mountain Galaxias (Galaxias olidus). A number of commonly occurring flow-dependent species also occur in riffles throughout the region, including a blackfly (S. ornatipes), dytiscid beetle (Platynectes decempunctatus), chironomid (Rheotanytarsus) and caddisfly (Cheumatopsyche). Any reduction in the extent and duration of flow from creeks and rivers where these species occur would threaten their continued survival and invariably lead to a worse condition rating being assigned in the future. Water quality effects such as increasing salinity, higher nutrient concentrations, excessive algal and plant growths, and blackened water from low oxygen levels could all contribute to the degradation of streams if flow patterns are reduced due to extractions and the placement of barriers.
Most streams in the region have severely degraded riparian habitats with, at best, a single line of River Red Gums or weedy tree such as willows and ash lining the banks over introduced grasses and weeds. The exception is where streams pass through conservation parks and the native trees and shrubs have been retained but in most cases the understorey is still being invaded by weeds and introduced grasses sourced from upstream agricultural lands.
Special environmental features
Many rare and sensitive species of macroinvertebrates were found in the region in 2011, including: various mites (e.g. Australiobates, Recifella, Albia, Koenikea and Piona); beetles (Simsonia leai and Sclerocyphon); blackflies (Paracnephia and Simulium melatum); thaumaliid flies (Austrothaumalea); chironomids (Harrissius, Apsectrotanypus, Stempellina and Harnischia); stoneflies (Illiesoperla mayi, Austrocerca tasmanica and Riekoperla naso); mayflies (Centroptilum elongatum, Nousia fuscula, Tasmanophlebia, Offadens, Thraulophlebia inconspicua and Atalophlebia species); and caddisflies (Apsilochorema gisbum, Ulmerochorema, Taschorema, Oxyethira, Anisocentropus, Lingora, Triplectides similis and a few specimens from the Family Tasimiidae). Many of these were found together from the sites that were assigned to the Very Good or Good condition ratings.
The only threatened species of fish recorded or seen during 2011 was the Mountain Galaxias although more extensive fish surveys in the region have also recorded other significant species such as Southern Pygmy Perch, Climbing Galaxias, Congolli, Freshwater Catfish and various eels and lampreys from many coastal catchments in recent years (Hammer et al. 2009).
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.|
|River Murray water discharges into some Mt Lofty Ranges rivers, introducing water of different quality and flow dynamics to the natural runoff (differences in flow timing, temperature, chemistry, nutrient and biological status).||SA Water will continue to work with the Adelaide and Mount Lofty Ranges NRM Board, Department for Environment, Water and Natural Resources and the EPA on catchment management programs to improve the water quality and environmental conservation status of river ecosystems. SA Water will continue best management practices on its landholdings in Mt Lofty Ranges catchment areas. SA Water will continue to monitor water quality in Mt Lofty Ranges catchments and manage its water transfers to minimise impacts on river bank stability.|
|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. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.