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Issues ConditionThreatening Processes |
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At a glance The issue Tasmania's water resources appear plentiful, but water availability varies considerably across the State and through time. In addition to climate-related variations and constraints, a variety of users and demands for water extraction affect water quantity and the availability of water to protect aquatic ecosystems in Tasmanian inland waters. Assessing water quantity and water use in Tasmania is necessary for the sustainable management of our water resources, which provide many social, economic and environmental services. This 'At a glance' section provides an overview of the water quantity and water use issue. More detailed information is available in the Water Quantity and Water Use Issue Report. Five indicators are included within this report. Several recommendations relevant to the issue of water quantity and water use are provided. Favourable news - There is reasonable knowledge about average water yields from medium to large catchments. This stems in large measure from long-term programs by Hydro Tasmania to track water yields for the State's Hydro generating capacity. An expanded network of stream gauging stations-an initiative under the Water Development Plan-will complement this established system.
- The ABS Water Account for Australia (ABS 2000) reported that Tasmania had the lowest mean household water usage of 176 kL/year. However, there is uncertainty about this information due to the potential for strong seasonal influences on these data and because of the lack of domestic metering to verify consumption on a more regular basis.
- Information on water is improving generally in Tasmania through the Water Development Plan, the expanded network of stream gauging stations across the State, the National Land and Water Resources Audit, and better dissemination of information through on-line products such as W.I.R.E.D (Water Information Resources and Electronic Data).
- The Water Management Act 1999 was introduced, providing for the sustainable use and development of water resources. The Act supersedes statutory water management provisions in 13 other Acts. All existing water entitlements have been converted to licences and allocations under the Water Management Act 1999.
- Capping of water usage occurred in the South Esk basin with further work done on the Great Forester River to cap use and prevent water creep. Proposals are being considered to extend this type of exercise Statewide. Installation of water meters has also occurred in the South Esk basin as part of water management planning.
- A new assessment process for dam construction permits under the Water Management Act 1999 has been established, which applies to both to small and large storage construction.
- There is still the opportunity in many of Tasmania's rivers to protect remaining environmental flows, provide for down-stream users, and avoid the problems of over-allocation that have occurred elsewhere. However, progress with water management planning will need to accelerate in order to move towards sustainability in water resource management.
Unfavourable news - Indicators show an increasing appropriation of water from the environment. Some broad measures of appropriation of water for human uses are detailed below.
- Water use for irrigation has grown by about 7% per annum since the last SoE Report (1997). This is on top of annual increases for irrigation water use, reported in the last SoE Report, of about 6% over the past four decades.
- Water extraction, and regulation through dams and storages, impacts on water quantity and quality with resulting implications for aquatic health. Further information on the implications of dam development for the environmental state of aquatic systems in Tasmania is contained in the Aquatic Health Issue Report.
- Since the last SoE Report, some 907 dams have been approved, although the majority of these are listed as having a dam status as 'proposed' rather than 'existing'. As at September 2002, the Water Information Management System database registered 5,516 existing dams (both in-stream and off-stream) for irrigation, stock, and stock and domestic uses.
- Some catchments have farm dam densities of nearly one dam for every square kilometre. The Northern Slopes bioregion in northern Tasmania (see map) has the greatest concentration of farm dams.
- Rivers in Tasmania are already often highly fragmented because of existing structures. Some of these structures are no longer serving an economic purpose, although the number of these structures is unknown.
- The National Land and Water Resources Audit assessed that 7 of the 19 Surface Water Management Areas were highly developed: Derwent, Gordon, King-Henty, Mersey, Pieman, Sandy Cape Coast, and Tamar. A four-class classification system was developed by the Audit to provide a simple method to communicate the status of Australia's water use and allocation in relation to sustainable water management. Highly developed indicates 70-100% allocation which, in Tasmania, reflects the importance of the State's hydro-generation system in these major catchments.
- Economics tells us that resources that are priced freely are typically consumed infinitely. Perhaps one of the most critical indicators for water-progress in metering and pricing of water to reflect full environmental costs-is not reported at all. Overall, the state of water metering and consumption-based pricing in Tasmania is relatively poor.
Uncertain news - The total area irrigated in Tasmania declined by a few thousand hectares to 51,738 ha in 1996-97. However, there are a number of potential explanations for this, ranging from seasonal variations to increasing irrigation efficiency to investment in higher capital irrigation equipment, and changes to higher value crops.
- The water quantity issue is generally subject to varying-but improving-information availability.
- The hydrology of small catchments (including some significant tributaries) is relatively unknown. Information is needed on the sustainable and divertible yield at a fine catchment scale. At these finer scales, the occurrence of water restrictions is one of the few 'measures' of rivers/regions under stress through water extraction. Some 22 rivers/regions were identified as being under stress during a typical dry summer.
- The lack of a continuous record of stream monitoring affects the capacity at a range of reporting scales to comment on trends and changes in water quantity and environmental flows. The Water Development Plan is intended to provide a stable long-term basis across Tasmania to monitor water flows and availability. The program of State of the River reporting has a significant contribution to make in improving information availability at these finer scales.
- Limited information is available on the type of irrigation systems installed on farms and the resulting environmental and/or production benefits.
- There is no integrated database on water infrastructure, which would include information on referable dams, farm dams, weirs and other in-stream structures.
- There is a significant lack of data on the extent to which land use activities contribute to changes in water quantity.
- A few Tasmanian industries have legislatively guaranteed water rights, and most industries are supplied by the metropolitan and regional utilities. As these generally have limited data, details on the breakdown of this class of water users are sketchy.
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