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Tuesday, 12 May 1970

Dr Gun asked the Minister for National Development, upon notice:

(1)   What is the maximum additional diversion of water which would be made possible to New South Wales and Victoria from the River Murray by the construction of the Dartmouth Dam.

(2)   To what use are New South Wales and Victoria expected to put the additional water thus diverted.

(3)   Has a cost-benefit analysis been carried out on the various projects on which New South Wales and Victoria will use the additional water.

(4)   What effect on salinity of the river in South Australia is expected from this additional water use in New South Wales and Victoria.

Mr Swartz - The answer to the honourmember's question is as follows:

(1)   The River Murray Waters Agreement provides that New South Wales and Victoria share the waters of the River Murray at Albury, and retain the right individually to the use of waters in tributaries below Albury. This has been modified by the incorporation into the River Murray Waters Agreement of the Menindee Lakes Agreement by which the River Murray Commission has the right to use a portion of that storage. The right of the two upstream States to use water as outlined above is conditional upon their making available to South Australia the entitlements of that State, which at present amount to 1.2S4 million acre feet per annum, and which will be increased to 1.3 million acre feet per annum when the Dartmouth storage becomes effective. Thus the amount of water available to the two upstream States is not defined by the Agreement as is the case with South Australia. Supplies available vary from year to year depending on inflow conditions, and water allocations are based on a study of the performance of the river and storage system using inflow records going back for about 63 years.

On the above basis, and assuming:

(a)   the two upstream States are restricted to not less than 70% of normal supplies under the worst conditions,

(b)   during periods of restriction available supplies are shared equally between the 3 States, as proposed when Dartmouth becomes effective. it has been calculated that -

1.   with the present storages, and South Australia's present entitlement of 1.254 million acre feet per annum, the total regulated supply available from the system is about 3.34 million acre feet per annum,

2.   with Dartmouth storage, and a South Australian entitlement of 1.3 million acre feet per annum, the total regulated supply available from the system is about 4.SS million acre feet per annum, an increase of 1.21 million acre feet per annum.

With regard to the sharing of this increase, after increasing South Australia's entitlement the two upstream States together will have an additional 960,000 acre feet of water per annum. Studies showed that Victoria would receive greater benefit from this increase than New South Wales because of the greater contribution made to the system by Victorian tributaries. However, as one of the conditions of the Agreement to proceed wilh Dartmouth, Victoria agreed to cede to New South Wales the right to the use of part of the Victorian tributary inflow, the effect of which is to equalise benefits received by the two States from the additional water available after Dartmouth becomes effective. Hence each State will receive substantially the same amount of additional water, namely 480,000 acre feet per annum.

(2)   The use of additional supplies made available by the works of the River Murray Commission is, of course, the responsibility of the individual States concerned and not of the Commission itself nor of the Commonwealth. However the following comments indicate the general pattern of expected water use.

It must be stressed that the additional supplies mentioned above are not in effect additional to present requirements for irrigation in the New South Wales and Victorian systems dependent on the River Murray. The Agreement to proceed with Chowilla in 1963 was based largely on the need for additional regulated flow in - order to avoid the necessity for unduly severe restrictions to existing supplies during dry periods. Hence, there is at this stage an urgent need for additional supplies in order to safeguard existing commitments, and this is particularly true in New South Wales. In Victoria there is more scope for provision of some additional supplies, and the Government has in fact already announced its intention to increase water allocations to existing irrigators in the Goulburn-Murray systems. In neither State is there likely to be any significant expansion of irrigation into new areas.

(3)   In the light of the information given above, there are not expected to be any significant projects, in the normal sense of that word, on which cost/benefit analysis could be carried out. As can be seen, the likely patterns of development involve many complex factors and detailed economic analysis would be a very difficult exercise. However some indication of the economy of the proposal is given by the fact that the additional water will be made available for a capital cost of approximately $30 per acre foot of additional water per annum, which is very low by present-day Australian standards. The attractiveness of the proposal is further enhanced by the fact that there is relatively little additional private or public capital involved in making use of this water in New South Wales and Victoria.

It might be added that the Dartmouth project is to replace another project, at Chowilla, previously approved by the 4 Parliaments, and has been shown by the results of published studies to be very much more attractive economically than the project it is replacing.

(4)   In general terms, it could be expected that additional diversions for irrigation in New South Wales and Victoria would result in some deterioration in water quality in the River Murray. However, as mentioned above, a considerable part of the additional water made available by the Dart- mouth project will be used to ensure that present commitments are met with reasonable reliability. The Dartmouth project will therefore not be accompanied by an expansion in irrigation development of the magnitude that might otherwise be expected, so that the effect on salinity in this case should be relatively small. Furthermore, the increase in South Australia's entitlement to water, after Dartmouth becomes effective, should be of particular value in this regard, because of the additional water available to that State in dry years when salinity tends to be more serious.

Detailed comment on this matter is expected to be included in the report which the River Murray Commission is expecting from its consultants on salinity within the next month or two. It seems likely that, as in the past, it will be necessary, as development of the water resources of the basin proceeds in the future, to pay continuing attention to operational and other measures to retain satisfactory quality in the lower Murray.

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