Australian Natural Resources Atlas

Natural Resource Topics

Water resources - Management and Development - Tasmania

Location map of SWMA Arthur River

Basin & Surface Water Management Area: Arthur River

Introduction

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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 Arthur River?

Use and Sustainable Yield

Comment about sustainable yield figure:

Sustainable yield was calculated by taking the difference between the annual median flow and the estimated environmental flow. The method of determingin the environmental flow is set out below

The NLWRA's Environmental Flows Method (for Use in The National Land and Water Resources Audit Only)

The following method has been developed for application in the Tasmanian section of the National Land and Water Resources Audit (NLWRA) only. While the method is broadly based upon that of Tennant (Tennant, 1976; also known as the Montana Method) it is only being used as an expedient means of assessing environmental water requirements for the Audit. The estimates should not be taken to represent true environmental water requirements.

Tennants method is based upon a consideration of annual average flow, basically allocating proportions of this flow to a summer and a winter period as average flow requirements for habitat maintenance. Various categories of narrative description (or habitat protection) have been used by Tennant to determine the appropriate proportion for a given purpose. His categories include Outstanding, Excellent, Good, Fair or Degrading, Poor or Minimum and Severe Degradation.

The method appears to provide elevated summer flows compared with those which might be expected in Australia possibly as a result of snow-melt dominance in America. These discrepancies appear to occur as the result of the application of proportions to annual average flows to estimate summer flow requirements.

In Tasmania the method has been used in a variety of modified forms including application of proportions to monthly or seasonal flow regimes. Results from these analyses have also been compared with more detailed estimates based upon the Instream Flow Incremental Methodology (Bovee, 1982). However, at this time there is insufficient information to adopt a particular narrative description category for common use. Indications are that an Excellent category may be suitable.

Under the NLWRA it is necessary to consider both an annual period of flows as well as a critical period. In Tasmania, the critical period for most purposes occurs over summer and has been adopted as December 1st to April 30th inclusive.

Issues in the adoption of a modified method are therefore:

  • What habitat protection category should be adopted?
  • Can we account for apparent summer flow discrepancies?
  • How can we make use of the results?

Habitat Protection Category

For the purposes of the NLWRA's Method the Good category has been adopted. This category has been adopted as a conservative means of identifying stressed river systems. While comparison of Tennant method estimates with IFIM estimates at a few sites indicates that an Excellent category could be chosen it is important to recognise the transient nature of the method adopted here.

Summer Flow Discrepancies

The apparent over-estimates of summer flow requirements using Tennants Method appear to arise as a result of the use of a proportion of annual average flow. The easiest way to overcome this is to utilise Tennants proportions on the relevant critical period flow. Since we are interested in the typical critical period flow, a median flow has been adopted rather than the mean. In many cases these figures will be similar, however, in stream subject to significant variations in flow median flows would always be preferred.

Use of the Results

The NLWRA's Method has been developed only for the purposes of the National Land and Water Resources Audit. Nevertheless, the estimates could also be used as a simple means of assessing the stress that river systems are under in Tasmania as an aid in the prioritising more detailed environmental flows work.

Summary of the Method

  • Identify the median critical period and annual flows for the area in question.
  • Adopt 30% of the annual flow as the recommended environmental water requirement to maintain good habitat.
  • Adopt 40% of the summer flow (Dec Apr) as the recommended environmental water requirement for that period.
  • Adopt 20% of the winter flow (May Nov) as the recommended environmental water requirement for that period.
  • If the critical period is different from summer or winter then adopt a weighted average of the relevant flows.

References

Bovee, K.D., 1982. A guide to instream habitat analysis using the instream flow incremental methodlogy U.S. Fish and Wildlife Service Biological Services Program FWS/OBS-82/26, Instream flow information paper 12. 248 p.

Tennant, D., 1976 Fisheries, Vol. 1, Issue 4 pp359 373

Sustainable yield (ML/yr):

1,919,386

Threshold year for sustainable year:

no data

Diversion Volume 1996 (ML):

21,627

Current resource development categorisation:

LOW DEVELOPMENT

Estimated in 2020

Estimated use in 2020(ML):

29,500

% change from 1996:

36

Resource development categorisation:

LOW DEVELOPMENT

Estimated in 2050

Estimated use in 2050(ML):

43,450

% change from 1996:

101

Resource development categorisation:

LOW DEVELOPMENT

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

Development Potential:

The principle 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 coarsness 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 Insitution 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 there future irrigation requirements generally supported this growth. 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 there affects on development potential in time for this Audit. At this stage there are no storages plaanned for this SWMA. It was assumed that domestic demand on a State and SWMA basis would remain static. Population growth has not been forecasted to 2050 and indeed ABS actually forcast 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.

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. Reliability of the 1.3 % growth is unknown and is further compounded by it being applied to approximate water use estimates for 1996/97.

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 forecast 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 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.

Current 2000Desired 2000Desired 2020Desired 2050

Management information

Scale of allocation planning

STATE/TERITORY

STATE/TERITORY

Inputs to allocation

BROAD RESOURCE INVESTIGATION

MODELLING AND RESOURCE

Type of monitoring - quantity

LIMITED OR NONE

BROAD-SCALE

Type of monitoring - quality

NONE

SALINITY AND OTHER LIMITED PARAMETERS

Distribution efficiency (H,M,L)

HIGH

HIGH

Use efficiency (H,M,L)

HIGH

HIGH

Resource management efficiency (H,M,L)

HIGH

HIGH

Degree of licensing

ALL MAJOR USES

ALL USES

Water trading (None, Limited, Significant)

NONE

NONE

Mechanism of trading

Volume traded (ML/yr)

no data

no data

no data

Number of transactions

Inter-basin transfers

LIMITED

SIGNIFICANT

Volume transferred (ML/yr)

no data

no data

no data

Environmental allocation category:

  • None
  • <33% of waterways with formal allocations
  • between 33% and 66% of waterways with formal allocations
  • >66 % of waterways with formal allocations

no data

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

Current Management Response:

Desired (Current) Management Response:

2020 Management Response:

See database

2050 Management Response:

See database

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

Assessment of Monitoring

Efficacy of the network:

Provided the gaps identified in the current network are rectified, the network will generally meet current requirements in the SWMA. However these will need to be reviewed and may need to be scaled up if further development estimated for the area 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:

There is 1 stream gauging station used in the SWMA. This station is the Arthur River d/s of Rapid River. The record for this station commenced in 1955. This site was a reference site for the State.

Water use in the SWMA is only approximate and there are no reliable records of water use for use in the Audit. In estimating water use it was assumed that the allocation represented water use.

There was no information available on database. for salinity However this may be available from other sources. However some information could be available from a number of private sources but could not be obtained in time for this Audit.

Current Gaps and Recommendations:

Data Gaps:

1. Information on water quality

2. Ongoing streamflow measuring station for area.

3. Water usage information Recommendations:

1. Establish an ongoing water quality and quantity measuring site for the area. Water quality to measure temperature, conductivity, turbidity and conductivity.

2. Carry out an annual water usage survey for the area.

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

Key

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