|
Issues ConditionThreatening Processes |
|
At a glance The issue Water quality is defined as a measure of the life sustaining nature of Tasmania's inland water resources and the potential of that water. It is the physical, chemical and biological condition of our waters, and the link between land and water use. Water quality is the integrator of the effects of our catchment management practices and the impacts of these on our estuaries and coastal zones. It is also a key indicator of sustainability (DPIWE 2003). This 'At a glance' section provides an overview of the state of water quality in Tasmania. More detailed information and references are available in the Water Quality Issue Report. The Issue Report presents data on two indicators: Exceedences of Water Quality Guidelines: Inland Waters and Land Cover. A recommendation is provided on Improving Water Quality, and several other related recommendations are also provided. While there are important relationships and overlaps between aquatic health and water quality, aquatic health is reviewed separately in this report (see Aquatic Health Issue Report). Water quality in this report is primarily concerned with physical-chemical measures while aquatic health is based on biotic measures, which synthesise and present an overarching perspective of river health. Drinking Water Quality is assessed separately as there are specific measures and responses in maintaining drinking water quality. Reporting on water quality needs to take into account the distribution of sampling sites available to present a whole-of-State assessment. Data from sampling sites available when compiling this report were often located in catchments with either little human impact or those with major impacts from mining. Data from the expanded network of water quality monitoring sites as shown in the map were not available. However, an improved sampling regime and distribution of sites will help to address these issues in the future. Environmental water quality is usually assessed against some criterion or guideline for each separate chemical or physical variable. The Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC & ARMCANZ 2000) have been used. Given sufficient data availability, these guidelines take into account regional variations in the environmental values of water quality, baseline environmental conditions and allow for variation in the parameters measured-and frequency of measurement-for each water body. Guidelines are chosen based on the primary management aims for that water body. Data used in this Issue Report were obtained from Hobart Water, DPIWE, Forestry Tasmania, Hydro Tasmania and Esk Water. Only monitoring sites which had greater than 24 samples taken between 1996-01 have been used. In addition, the Case Study on Waterwatch water quality monitoring in Tasmania presents the monitoring results of some of the 150 groups involved in monitoring water quality within Tasmania as part of the Waterwatch program. A Case Study is also included on the King River, which updates understanding of the condition of the river and current treatment measures (see King River Case Study). Favourable news- Few exceedences of the ANZECC (2000) aquatic ecosystem guidelines (adapted for Tasmanian conditions) were recorded for turbidity in the forested sites of the Southern Forests compared with data from the rest of the State.
- Hydro Tasmania undertakes extensive monitoring of water around Tasmania. It monitors 50 sites, covering 15 lakes and 14 rivers for water quality and river flow. This is achieved through regular site visits plus telemetered continuous monitoring of parameters.
- Monitoring on a catchment scale occurs through State of Rivers reporting - DPIWE, with water quality data available at W.I.R.E.D. A Tasmanian Water Quality Monitoring Strategy has been prepared by DPIWE to respond to the need for a co-ordinated system for the collection, collation and reporting of water quality information.
- The Board of Environmental Management and Pollution Control has been setting Protected Environmental Values (PEVs) for surface waters since early 1999 as required by the State Policy on Water Quality Management 1997. Through the water infrastructure program in Tasmania, new water quality and water flow monitoring site installations are occurring.
- The Waterwatch program participants sample a total of 650 sites in 70 rivers throughout the State. Waterwatch water quality monitoring includes data collection for pH, dissolved oxygen, conductivity, temperature and turbidity. Waterwatch groups are influencing local communities and government in a variety of ways, and examples are provided in Waterwatch water quality monitoring in Tasmania.
- Some catchments in the west and south-west of the State are well-reserved and well-protected from land cover change and native vegetation clearance. These factors are considered to have a primary influence on the water quality of the associated receiving waters. Catchments in the south-west and west of the State indicate a relatively pristine condition evidenced by less of their catchment areas under 'modified' land cover classes. These catchments include Port Davey, Wanderer-Giblin, and Gordon-Franklin. A number of east coast catchments have maintained relatively high percentage catchment areas under 'natural' land cover (less than 20% modified): George, Swan-Apsley and Prosser. In the south-east, the Huon catchment also maintains a relatively high percentage of natural land cover.
- Larger rivers had low exceedence levels for pH. The percentage of samples exceeding primary recreation pH guidelines was zero for all sites. The percentage of samples exceeding irrigation pH guidelines was variable.
- A toxicological evaluation of the acid mine drainage wastewater was conducted in 2000 to assist in determining treatment options at Mt Lyell. The primary aim is to rehabilitate the ecosystems in the lower King River (down stream of the junction with the Queen River) and the upper Macquarie Harbour. The principal findings of the trials are that treatment of acid drainage is likely to lead to some recovery of macroinvertebrate communities in the lower King River and the potential recovery of fish populations in the lower King River provided other factors-such as sediment toxicity and undesirable variation in flows from power station operation-do not impede recovery.
Unfavourable news - Turbidity: Sites with higher turbidity guideline exceedences were typically those surrounded by agricultural land (e.g. Pipers and Brid rivers) or impacted by mining (e.g. Savage River sites), and compared poorly to streams with forested catchments such as the Crystal, Swanson and King rivers. Prolific algal growths resulting from high water nutrient levels have been noted at sites such as the Pipers and Brid rivers. Medium level exceedences occurred at Tahune, Bren, Johns and Leigh sampling sites.
- Conductivity: the percentage of measurements exceeding aquatic ecosystem guidelines was high for Brid, Cook, Piper, Leigh, Johns, Lune Lower, Savage River Station, and Huskisson river sampling sites. Conductivity guideline exceedences typically occurred during periods of low flow. Conductivities also tend to increase along the length of the river as it approaches the coast. Medium level of exceedence occurred at the Huon River.
- pH: the percentage of measurements exceeding aquatic ecosystems guidelines were high for all smaller, upland rivers. Surface waters within the Lake Pieman catchment had high levels of guideline exceedences (with the exception of the Huskisson River which was lower). Moderate levels of guideline exceedences occurred at the Savage River sites.
- Metals: within the Pieman and Savage River mining areas various guideline exceedences occurred for aluminium, cadmium, copper, chromium, manganese, nickel, lead, zinc, and iron. Little monitoring of the King River has occurred, as the key focus of monitoring efforts by the State Government has been water quality in the receiving waters in Macquarie Harbour.
- A number of management catchments ranked poorly because they had a high percentage of their catchment area experiencing woody vegetation change (a measure of land cover disturbance) and a high percentage of their area under modified land cover classes (such as agricultural and urban land cover). These management catchments include the Cam, Inglis, Blythe, Rubicon, Leven, Montagu and King Island.
- Urban and suburban land use represent a substantial modification of land cover, with significant flow-on impacts for catchment condition. The five catchments with the highest percentage area under urban and suburban land use are Lower Derwent, Derwent Estuary-Bruny, Cam, Tamar Estuary, and North Esk.
- While the establishment of W.I.R.E.D (public access to water information) is significant, there is still no active, centralised and regularly updated database for collecting and disseminating water quality information for all water-related agencies.
Uncertain news - There are uncertainties with the state of water quality in Tasmania due to the limited availability of data, a concentration towards minimally disturbed sites, and the under-representation of agricultural and urban areas.
- There are also many unknowns about the groundwater resource and interactions between surface and groundwater quality
|
|
