Page 4906 - Week 15 - Thursday, 8 December 1994

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MINISTER FOR URBAN SERVICES

LEGISLATIVE ASSEMBLY QUESTION

QUESTION NO 1495

Water Storage Facilities

Mr Cornwell - asked the Minister for Urban Services - in relation to Canberras water storage facilities:

(1) Has consideration been given to raising the height of our existing dams,

as has been done elsewhere in Australia

(2) If so, (a) which dams could be enhanced by such a process and (b) how

much extra water could they store.

(3) If not, why not.

Mr Lamont - the answer to the Members question is as follows:

(1) I am able to confirm that raising our existing dams was looked at in the

development of the Future Water Supply Strategy, and found not to be a

viable option.

(2) (a) The only possible exception to this is the Cotter dam, which was

identified in the Future Water Supply Strategy. However, I understand

that this would require completely rebuilding the existing dam as the old

Cotter Dam wall has previously been raised during its lifetime.

(b) The existing Cotter Dam has a storage capacity of approximately 5 gigalitres (GL) of water. A rebuilt Cotter Dam could be expected to store approximately 30 GL, or 3000 megalitres.

(3) Our existing water supply dams have been designed to take the optimal

yield from their respective catchments. Raising these dams will

effectively result in negligible additional storage at very high costs.

While this extra storage would remain empty most of the time, it would

effectively retard those significant floods which might cause the dams to

overflow. This would deprive the rivers of occasional flushes, and so

could in fact lead to increased blue-green algal growth problems down

stream of the dams.

4906

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