Introduction

As resource demands and pressure increases so to do the requirements of both management and information needs. Outlined below are the key issues facing the region as determined by the State / Territory water management agency.

What is the estimated demand for surface water in Mersey River?

How was this assessment undertaken in the Mersey River Surface Water Management Area?

Development Potential:

The principal data source currently available to the State for use in assessing development potential for irrigation is farm dam growth. Unfortunately this information could not be broken down to a surface water management area (SWMA) level but was only available on a State scale. Due to the coarseness of this information it was not considered to be particularly suitable as a tool at SWMA level for estimating growth. The other source of information available was from a joint study project by the Australian Academy of Technological Science and Engineering and the Institution of Engineers Australia titled "Water and the Australian Economy April 1999"(ISBN 1875618 50 3). This report arrived at a growth rate of 1.3 percent for Tasmania. It was found that the information available on farm dam growth inn the State and some landholder estimates in relation to their future irrigation requirements generally supported this growth. In the Mersey a survey of irrigation water use was undertaken in 1999. This survey invited irrigators to project their usage to the year 2010. This estimate amounted to 16460 megalitres per annum. Currently in the State there are a number of proposals for large storage development. These are all at a very preliminary stage and information cannot be made available on their affects on development potential in time for this Audit. At this stage there are no storages planned for this SWMA. It was assumed that domestic demand on a State and SWMA basis would remain static. Population growth has not been predicted to 2050 and indeed ABS actually forecast a negative growth. Industrial growth cannot be forecast accurately either at a State or SWMA level with any degree assurity at this stage without further studies. It is envisaged that growth will occur in the State but reliable data is not available to predict with any degree of accuracy. Currently it is estimated that 8000 megalitres is taken out annually for industry .

Estimated Use:

Developed potential for use was assessed on the basis of a 1.3 percent growth rate applied to the use estimate for 1996/97 of 16460 at 2010 and projected to 2050. A flat 8000 megalitres per annum was added to the projected irrigation amount at 2020 and then again at 2050.

Reliability of the 1.3 % growth is unknown and is further compounded by it being applied to approximate projected use figure for 2010. In addition no allowance was allowed for industrial development which was also a low reliability assessment.

Category could not be determined due to the absence of sustainable yield estimate (see comments made earlier in document).

Developed Yield:

Details on potential infrastructure development were not available for use in the Audit. However for the purposes of the Audit, the assumption adopted was that infrastructure could be developed to meet the demand forecast. Hence developed yield for years 2020 and 2050 were taken as the forcast use rounded up to the next 1000 megalitres.

Management goals and objectives:

1 Essential needs of town water supplies and stock and domestic needs, 2 Ecosystem needs.

3. Water for Hydro Electric Corporation, 4 Supply of water for irrigation and non essential town supply purposes eg parks and gardens,

See TAS Water Resources Assessment 2000 Report and Water Resources Assessment 2000 Technical Report for comment on methods and assumptions.

Comments on Management Responses in the Mersey River Surface Water Management Area

Current Management Response:

Desired (Current) Management Response:

2020 Management Response:

2050 Management Response:

See TAS Water Resources Assessment 2000 Report for comment on management responses.

Assessment of Monitoring

Efficacy of the network:

A considerable degree of monitoring work is being undertaken in the Mersey SWMA by both the Department of Primary Industries, Water and Environment and Hydro Electric Corporation.

There are a number of gaps in the monitoring network. These are being examined as part of the current water planning work underway in the area which is aimed at developing water management plans and improved water allocation arrangements.

At this stage it would be premature to report further on the efficacy of current networks until the outcome of the current work is realised.

Data management requirements:

All information from streamflow monitoring stations will need to be put into streamflow database (Hydrol) and water allocation and usage information put into the Water Information Management System data base (WIMS). These two systems need to be linked to GIS to provide a better managemen focus for this data.

Work will be required to gather water quality information collected from a multitude of sources in the State and placed in the Hydrol data base. In addition, rationalising the collection of current water quality information from these sources will be required to make the process more strategic and effective from both a cost and assessment perspective.

Protective management:

Current methods used in relation to these catchments should be satisfactory. Methods allow for assessment of current arrangements and for these to be modified as required.

Options for monitoring:

There is a clear need for Commonwealth assistance under some form of partnership arrangement with the State to provide resources to address information gaps. This would better position the State for providing better information for future Audits

See TAS Water Resources Assessment 2000 Technical Report for an assessment of monitoring

Data Availability, Gaps and Recommendations

Data Availability:

Stream gauges are located at various sites throughout the catchment. The records used in this audit were; Mersey River at Kimberley, Mersey River at Liena, Fisher a/b Mackenzie, Mersey a/b Arm, Don River u/s Old Bass Highway and Mersey River at Latrobe

Current Gaps and Recommendations:

Data Gaps: The following have been identified as gaps in data:

1. Assumptions used in Review 85 for determining divertible yield;

2. No yield for HEC system available

3. Information on sustainable yield not available;

4. No natural mean annual flow available.

Recommendations:

1. Re estimate divertible and developed yield for the SWMA.

2. Estimate sustainable yield for SWMA.

3. Review and where appropriate ugrade water quality monitoring stations.

Future Gaps:

To properly estimate future demands would require very detailed analysis and take considerable time. Such estimates would be subject to changes in market forces, community expectations and government policy change.

All estimates of developed yield and growth provided in this report are very approximate and are not generally considered to be satisfactory at this stage for long term planning for the State. It was assumed that the developed yield could be met by water infrastructure developments. However investigations into appropriate developments could not be undertaken in time for the Audit which is a very clear gap in information. For the purpose of long term planning a more rigorous estimate for long term growth would have to be made.

From a water resource development viewpoint, Tasmania is commencing the start of another growth period with considerable interest in irrigation expansion and storage development. Unfortunately estimates of this likely growth could not be made in time to meet Audit deadlines.

See TAS Water Resources Assessment 2000 Technical Report for a review of data availability,gaps and recommendations.

Further information

• Tasmania Water Resources Assessment 2000 Technical Report
• Link to data available for download on the Surface Water Management Areas
• Link to the Map Maker to make a map using this information.