The ACT government wants to clean up Canberra's lakes, but back in 1985 federal cabinet was told Lake Tuggeranong's primary purpose would be to protect the Murrumbidgee River from urban pollution.

In November 1985, Territories Minister Gordon Scholes briefed cabinet on the proposed response to a parliamentary committee inquiry into the Murrumbidgee River in the ACT region.

The committee report acknowledged that environmental protection of the river was needed to ensure adequate water supplies for the ACT and downstream NSW towns.

Mr Scholes said that the development of the Tuggeranong Valley was already damaging the health of waterways.

''Urban run-off from Tuggeranong has already caused considerable pollution of the Murrumbidgee River,'' Mr Scholes said in a cabinet submission.

The major pollution control item proposed for 1986-87 was the $13.5 million construction of Lake Tuggeranong. While it would have recreational and aesthetic benefits, its primary purpose would be to protect the river.

''The primary design objective of this lake is to provide an interception facility to protect the Murrumbidgee River, although the dam itself provides the main road access to the town centre and there will be aesthetic and recreational benefits,'' Mr Scholes said.

''In this respect the Tuggeranong Creek catchment contains 65 per cent of the total proposed Tuggeranong urban development.

''The location of a major Lake at the foot of this catchment provides a substantial retention basin for the interception of urban run-off pollutants. Lake Tuggeranong is expected to retain 100 per cent of transported sands and gravels, urban rubbish, 70 per cent of nutrients and suspended solids, and 99 per cent of bacteria discharged in urban run-off within its catchments.''

Fast forward 30 years and the health of Canberra's three main lakes was an issue at the recent ACT election, with the major parties promising policies to decrease contamination from run-off.