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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Water resources - Availability - Tasmania
Tasmania
Tasmania Overview
Tasmania represents only 0.9% Australia's land area and supports around 3% the population, yet the State has 12% the nation's total freshwater resources.
The annual water resource available in Tasmania is 44,800 GL from surface runoff and 2,500 GL from groundwater. This represents a significant water resource and supports the requirements of town water supply a developing and viable irrigation industry and most of the State's power requirements.
Expansion for new consumptive purposes now has to largely rely on storing the plentiful winter stream-flows for later use during summer or use of groundwater. To store surface water, there are a number of private proposals in the State seeking approval for large storage construction.
Water management in Tasmania is now moving into a new era with the enactment of the Water Management Act 1999. This Act came into force on 1 January 2000. These include defined water allocations for all users, allocations of water for ecosystem protection, water management planning and a system of tradeable water property rights.
Surface Water Reporting Units
The Australian Water Resources Council (AWRC) basins were the reporting units identified for Tasmania. A conscious decision was made not to break these basins down further as realistic water usage and environmental water provisions would not be available in time for the Audit.
It is anticipated that for future water audits, programs currently under way in the State will be able to provide information at a finer level of detail. These programs include state of the river reporting, estimation of environmental water requirements and water management planning.
The catchment reporting unit structure currently being developed for the State amounts to 48 catchments an increase of 29 over the AWRC number. These catchments will form the basis of water management planning in the State.
Groundwater Reporting Units
The State was divided up into 14 Groundwater Management Units (GMUs) and 3 unincorporated areas.
For further information contact Tasmanian Department of Primary Industries, Water and Environment at www.dpiwe.tas.gov.au.
How much surface water does Tasmania have?
Hydrology
The mean annual runoff of the State is 44,842 GL. Approximately 12 % of Australia's runoff occur from Tasmania, which represents only 1% of the total land area of the continent. Based on this figure it would appear that Tasmania's surface water is more than adequate. However the State's developed areas experience regular dry summer periods when water demand can be greater than natural streamflows. Under these situations water extractions are restricted from rivers and streams to protect environment needs and those of stock and domestic users. The most notable example of water restrictions occurred during the year 2000 when substantial areas in the north of the State either had total or partial ban on taking of irrigation water from January to March.
There is a strong runoff gradient in the State from West to East. The average annual rainfall in the midlands is approximately one sixth of the on the west coast and run-off varies form 80-90% in the Pieman River area to only 10-15% in the Coal River.
Available Resource
The total estimated divertible surface water resource for Tasmania was taken from the Review 85 estimates. This estimate represents approximately 28% of the total streamflow. It must be stressed that this figure is only an estimate and could be varied subject to a more detailed analysis being undertaken.
The estimated 'non-divertible' portion of the total surface water resource refers to water that is unable to be used for development for reasons such as high cost, environmental or social factors. It must also be emphasised that the total volume of divertible yield does not account for environmental water provisions and hence should not be taken as a true reflection of the amount of water that can be made available for development.
The sustainable yield has been determined as the maximum volume of water that can be made available after making an estimation and taking account of in-stream environmental water requirements. For Tasmania, the total estimated sustainable yield was not available for all SWMAs as these estimates could not be finalised for Hydro Electric Corporation catchments in time to meet Audit deadlines. However the estimate was made for 13 or 70% of SWMAs giving a sustainable yield of 17,989 GL per annum representing 66% of the total streamflow in these areas. Of the sustainable yield in these thirteen SWMAs, 2 percent (or 1.3% of the streamflow) has already been developed for use. If the critical period sustainable and developed yield are examined on an individual SWMA basis, this amount approaches 50% mined.
For the 13 management areas where sustainable yield has been estimated, the most highly developed surface water resource is the Tamar Basin, with a developed yield of 120 GL. This represents 35% of the total developed yield for these 13 surface water management areas in the State.
It must be noted that the sustainable yield is not necessarily a good indicator of the water that could be utilised due to the physical inability to take advantage of that water. In Tasmania, it is estimated that the sustainable yield could be as much as 6 times the estimated divertible yield on an annual basis.
| Basin/Surface Water Management Area | Mean Annual Run-off (GL/yr) | % of state | Natural mean annual out-flow (GL/yr) | In-flow (GL/yr) |
|---|---|---|---|---|
| Arthur River | 2,789 | 6.12 | 2,810 | 0 |
| Coal River | 55 | .12 | 56 | 0 |
| Derwent River | 4,822 | 10.58 | 4,822 | 0 |
| East Coast | 1,819 | 3.99 | 1,834 | 0 |
| Flinders - Cape Barren Islands | 215 | .47 | 216 | 0 |
| Forth River | 2,107 | 4.62 | 2,107 | 740 |
| Gordon River | 6,279 | 13.77 | 6,279 | 1,381 |
| Huon River | 3,658 | 8.02 | 3,669 | 0 |
| King Island | 254 | .56 | 254 | 0 |
| King-Henty Rivers | 2,206 | 4.84 | 2,206 | 0 |
| Kingston Coast | 263 | .58 | 270 | 0 |
| Mersey River | 1,269 | 2.78 | 529 | 0 |
| Pieman River | 1,899 | 4.16 | 1,899 | 201 |
| Piper-Ringarooma Rivers | 1,457 | 3.19 | 1,518 | no data |
| Rubicon River | 200 | .44 | 210 | no data |
| Sandy Cape Coast | 813 | 1.78 | 813 | 0 |
| Smithton-Burnie Coast | 3,177 | 6.97 | 3,267 | 0 |
| South-West Coast | 8,724 | 19.14 | 8,724 | 0 |
| Tamar River | 3,586 | 7.87 | 3,863 | 639 |
How saline are Tasmania's surface water resources?
Table: Surface water resource by salinity class for divertible yield (GL)
| Surface Water Managemnet Area | <500 mg/l (GL/yr) | 500 - 1500 mg/l (GL/yr) | 1500 - 5000 mg/l (GL/yr) | 5000 -14000 mg/l (GL/yr) | >14000 mg/l (GL/yr) | Total volume (GL/yr) |
|---|---|---|---|---|---|---|
| Tasmania | 6,696 | no data | 10 | no data | no data | no data |
| Arthur River | no data | no data | no data | no data | no data | no data |
| Coal River | no data | no data | 10 | no data | no data | 10 |
| Derwent River | 1,205 | no data | no data | no data | no data | 1,205 |
| East Coast | 348 | no data | no data | no data | no data | 348 |
| Flinders - Cape Barren Islands | 27 | no data | no data | no data | no data | 27 |
| Forth River | 331 | no data | no data | no data | no data | 331 |
| Gordon River | no data | no data | no data | no data | no data | 5,460 |
| Huon River | 1,416 | no data | no data | no data | no data | 1,416 |
| King Island | no data | no data | no data | no data | no data | 29 |
| King-Henty Rivers | no data | no data | no data | no data | no data | 1,786 |
| Kingston Coast | no data | no data | no data | no data | no data | 17 |
| Mersey River | 1,090 | no data | no data | no data | no data | 1,090 |
| Pieman River | no data | no data | no data | no data | no data | 1,130 |
| Piper-Ringarooma Rivers | 309 | no data | no data | no data | no data | 309 |
| Rubicon River | 41 | no data | no data | no data | no data | 41 |
| Sandy Cape Coast | no data | no data | no data | no data | no data | 84 |
| Smithton-Burnie Coast | 704 | no data | no data | no data | no data | 704 |
| South-West Coast | 875 | no data | no data | no data | no data | 875 |
| Tamar River | 350 | no data | no data | no data | no data | 350 |
How much of Tasmania's surface water resource has been developed?
Unlike other States, Tasmania is unique in that most of its water supply systems are used for hydropower generation purposes. There are 6 major hydropower developments in the State. These are Great Lake-South Esk, Derwent-Nive, Pieman-Anthony, Mersey-Forth, King-Lake Margaret, and Gordon-Pedder. In addition to hydropower, there are 3 systems supplying State run irrigation areas as well as a multitude of water supply systems from which regional water authorities and councils take their water.
The Tasmanian State the Government is currently encouraging private developers to increase irrigation production. As a consequence, there are a number of private storage investigations underway looking at the provision of additional water for irrigation purposes. These investigations are generally at a preliminary stage and firmer details could not be made available for the Audit.
There are over 48 storages (with a volume capacity exceeding 1500 ML) located across the State. These represent a total storage capacity of 26,223,000 GL for Tasmania. Of these storages, Lake Gordon comprising a capacity 12,450 GL is the largest storage in Australia.
How committed are Tasmania's surface water resources?
There are no over-developed management areas on an annual basis on SWMA scale. However if the critical period was examined on a component area basis, indications are that there could be at least two which would be classed as overdeveloped in accordance with the Audit criteria. This issue is presently being addressed by the State through its water management planning and environmental water provision work. However, the level of detail is not significantly progressed to allow reporting under the Audit.
In relation to category 2 to 3 catchments indications are that some component areas of SWMAs would fall into these categories during the critical period. However, due to the inaccurate information available on water usage at a component area scale and the early stage of work in progress to determine environmental water requirements and provisions, this has not been reported on.
The estimated total volume of water available (sustainable yield less the total annual use) for development for 13 of the States 19 SWMAs is approximately 17,500 GL. This has been estimated based on the following assumptions:
- No account is made of 6 of the States 7 SWMAs used for commercial hydro electric power;
- Some SWMAs component catchments areas are located in largely wilderness and or World Heritage Areas and are unlikely to be developed;
- Water for development will largely be made available from Tasmania's abundant winter flows and would need to be taken into storages for later use during the normally dry summer period. This amount will be dependent on the efficiency of capture and degree of regulation.
Note: In the table below, the figures include the volume of water diverted for use in hydro-electric power generation in the Tamar River Basin, the Gordon River Basin, the Pieman River Basin and the Forth River Basin.
| Basin/SWMA | Volume diverted (GL/yr) | Sustainable (GL/yr) | Diversion Development class |
|---|---|---|---|
| Arthur River | 22 | 1,920 | LOW DEVELOPMENT |
| Coal River | 4 | 27 | LOW DEVELOPMENT |
| Derwent River | 751 | no data | HIGH DEVELOPMENT |
| East Coast | 15 | 1,184 | LOW DEVELOPMENT |
| Flinders - Cape Barren Islands | 1 | 122 | LOW DEVELOPMENT |
| Forth River | 15 | no data | MEDIUM DEVELOPMENT |
| Gordon River | 0 | no data | HIGH DEVELOPMENT |
| Huon River | 1,384 | 2,510 | MEDIUM DEVELOPMENT |
| King Island | 1 | 153 | LOW DEVELOPMENT |
| King-Henty Rivers | 205 | no data | HIGH DEVELOPMENT |
| Kingston Coast | 7 | 170 | LOW DEVELOPMENT |
| Mersey River | 760 | no data | HIGH DEVELOPMENT |
| Pieman River | 9 | no data | HIGH DEVELOPMENT |
| Piper-Ringarooma Rivers | 53 | 985 | LOW DEVELOPMENT |
| Rubicon River | 10 | 138 | LOW DEVELOPMENT |
| Sandy Cape Coast | 0 | no data | HIGH DEVELOPMENT |
| Smithton-Burnie Coast | 90 | 2,138 | LOW DEVELOPMENT |
| South-West Coast | 1 | 6,154 | LOW DEVELOPMENT |
| Tamar River | 92 | 2,057 | HIGH DEVELOPMENT |
The volume diverted is the total volume of the SWMA's surface water resources diverted for use both within the management area and for export to other management areas.
A four-class classification system was developed to provide a simple method to communicate the status of the use and allocation of Australia's water resources in relation to sustainable water management.
It is important to recognise that adequately quantifying a sustainable flow regime or sustainable yield and consequent operating rules is a complex matter. State, Territory and scientific agencies continue to develop and apply methods and measures for determining sustainable flow regimes and sustainable yields.
This categorisation provides a general guide only. Please refer to the State and Territory Overview and Technical reports for detail on the analysis methods used.
| Category | Development status | |
|---|---|---|
| 1 | <30% | Low development |
| 2 | 30 - 70% | Moderate development |
| 3 | 70 - 100% | Highly developed |
| 4 | 100% | Overdeveloped |
* Water use as a percentage of sustainable flow regime (surface water) and sustainable yield (groundwater)
How much groundwater does Tasmania have?
Hydrogeology
Groundwater resources within Tasmania can be broadly divided into four categories:
- Palaeozoic to Mesozoic fractured sedimentary and igneous rocks. The fractured rock aquifers comprise the largest area and provide widespread potential for stock and urban supplies but have limited potential for agricultural irrigation purposes.
- Tertiary and younger sedimentary rocks and basalts deposited in discrete basins: Major Tertiary sedimentary basins include the Port Sorell - Sassafras, Scottsdale and Longford Basins. Groundwater is extracted from both the sedimentary sequences (sands and conglomerates) and the inter-layered basalts.
- Tertiary age basalts: Basalt plains, such as those around Burnie and Sorell, also form significant groundwater resources.
- Coastal dune systems: Several important groundwater resources have been identified within coastal dune systems. Examples are Landherne and Tomahawk areas.
With the exception of some small urban supplies, the majority of the GMUs defined within Tasmania are within the Tertiary and Coastal hydrogeological settings.
Available resource
In total, approximately 2,500 GL of groundwater is available for extraction from the groundwater systems in Tasmania. Much of this occurs in fractured rock aquifers, limiting the potential for development due to low yields of individual bores. The major useable groundwater resources are contained within the Groundwater Management Units, accounting for approximately 312 GL/yr.
Sustainable Yield and Environmental Allocation
Currently there is no formal allocation for environmental groundwater use. For the majority of areas, the current level of development represents only a small percentage of the total resource and is unlikely to have a detrimental impact on the environment. With further development, formal allocations may be required in order to protect significant environmental values.
How committed are Tasmania's groundwater resources?
Table: Allocation volumes (GL/yr in each development category)
Note: "GMU"=Groundwater Management Unit "UA"=Unallocated Area
| Province | Over | High | Med | Low | Total (GL/yr) | |
|---|---|---|---|---|---|---|
| Tasmania 1 | GMU | no data | no data | no data | 3 | 3 |
| UA | no data | no data | no data | 2 | 2 | |
| Tasmania 2 | GMU | no data | no data | 3 | 2 | 5 |
| UA | no data | no data | no data | 11 | 11 | |
| Tasmania 3 | GMU | no data | no data | no data | 1 | 1 |
| UA | no data | no data | no data | 1 | 1 |
A four-class classification system was developed to provide a simple method to communicate the status of the use and allocation of Australia's water resources in relation to sustainable water management.
It is important to recognise that adequately quantifying a sustainable flow regime or sustainable yield and consequent operating rules is a complex matter. State, Territory and scientific agencies continue to develop and apply methods and measures for determining sustainable flow regimes and sustainable yields.
This categorisation provides a general guide only. Please refer to the State and Territory Overview and Technical reports for detail on the analysis methods used.
| Category | Development status | |
| 1 | <30% | Low development |
| 2 | 30 - 70% | Moderate development |
| 3 | 70 - 100% | Highly developed |
| 4 | 100% | Overdeveloped |
* Water use as a percentage of sustainable flow regime (surface water) and sustainable yield (groundwater)
How saline are Tasmania's groundwater resources?
Table: Groundwater resource by salinity class
| Province | <1500 mg/l (GL/yr) | 5000 mg/l (GL/yr) | 14000 mg/l (GL/yr) | >14000 mg/l (GL/yr) | Total volume (GL/yr) | |
|---|---|---|---|---|---|---|
| Tasmania | GMU | 270342 | 38322 | 449 | 3039 | 312152 |
| UA | 1315046 | 728383 | 175191 | 2218620 | ||
| Tasmania 1 | GMU | 195,000 | no data | no data | no data | no data |
| UA | 1,316 | no data | no data | no data | no data | |
| Tasmania 2 | GMU | 33,444 | no data | 1 | 4 | no data |
| UA | no data | 729 | no data | no data | no data | |
| Tasmania 3 | GMU | 41,898 | 39 | no data | no data | no data |
| UA | no data | no data | no data | 176 | no data |
How much water does Tasmania trade?
The Total reported Volume Traded in Tasmania is 0 GL; in 0 transactions.
The State and Territory water management agencies continue to consider water use efficiency and optimisation strategies within existing infrastructure (e.g. water supply efficiency, precision irrigation and scheduling, water recycling, trading and pricing) as part of water resource development planning.
Recognising that water is a finite resource, the States and Territories have developed water allocation systems where security and reliability are assigned to entitlement, trading is provided so water can be moved to high value uses and the choices of individuals are maximised.
Part of the decision-making framework to enable and facilitate water trading, changes in water allocation and definition of rights to water is the need for water use monitoring. Water use monitoring will assist decision-making and provide an opportunity over time to evaluate the effectiveness of allocation policies.
Environmental water requirements
Tasmania like all other States and Territories in Australia is committed to assessing the environmental water requirements for river systems and making environmental water provisions for these. The State is developing these based on the National Principles for the Provision of Water for Ecosystems (ARMCANZ & ANZECC, 1996)
A great deal of work has progressed in assessing environmental water requirements. In addition very good progress is being made towards the development of water management plans for rivers and streams. As a minimum, these plans are required to include an assessment of the water needed by ecosystems. They will put into place the environmental water provisions.
The State is currently developing a policy on water for the environment as well as a preliminary method for estimating summer environmental flows in unstressed Tasmanian rivers. Methodologies to be used under the draft policy depend on whether the stream is stressed, regulated or unregulated.
Licensed water allocations have been capped on most rivers and streams in the State over the critical period December to April. The only exceptions are those where the consumptive demand is very small in relation to available flows. However on these rivers, an upper limit to protect the environment has been set for additional consumptive use pending the implementation of environmental water provisions.
In relation to groundwater at present there is no formal assessment of requirements to support environmental needs. Impacts are assessed on an as needed basis
Further information
- Tasmania Water Resources Assessment 2000 Report
- Tasmania Water Resources Assessment 2000 Technical Report
- report from the study of Streamflow data and modelled streamflow
- Link to data available for download on the:
- extension of unimpaired monthly streamflow data and regionalisation of parameter values to estimate streamflow in ungauged catchments (NLWRA 2000)
- Surface Water Management Areas
- Groundwater management units and provinces - ARC/INFO export
- Link to the Map Maker to make a map using this information.
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