Maxine Cooper has also announced her office is proposing audits of the Capital Metro light rail project, Canberra's jail and the management of capital works projects.

In a report outlining her proposed audit program for 2013-14, Dr Cooper said planning was already under way for an examination of the massive dam expansion project.

"Expenditure on the enlarged Cotter Dam is expected to be around $409 million, against an initial estimate of approximately $145 million for the construction of the dam and associated works,'' she said. "The audit could examine the management of the enlarged Cotter Dam project.

"This may include consideration of the efficiency and effectiveness of the implementation of the project, particularly with respect to the delivery of the project against original budget expectations. Communication processes could also be considered.''

The 78-gigalitre-capacity expanded Cotter Dam is operational but works are still being carried out.

The Liberal opposition and the engineers' union have both raised concerns about cost increases.

Opposition Leader Jeremy Hanson welcomed Dr Cooper's decision to audit the expanded dam and other capital works projects.

"The ACT capital works program is infamous for cost blowouts and delays, including the iconic failure that was the Gungahlin Drive extension delay and duplication,'' Mr Hanson said.

"The Canberra Liberals welcome the forthcoming audits and hope that the Auditor-General is able to uncover the full picture that we have been calling for so long to be revealed, and that the Labor-Green government has been so anxious to cover up.''

Chief Minister Katy Gallagher and Treasurer Andrew Barr are the official shareholders in the publicly owned ACTEW Corporation, which is responsible for the dam.

Ms Gallagher said she and Mr Barr had been open and transparent about revised costings for the dam following advice from ACTEW.

"The government acknowledges the size and complexity of the project along with the external factors which have impacted on the project over the last two years,'' Ms Gallagher said.

"The enlarged Cotter Dam is an important part of ensuring Canberra's water security into the future and we are ready to assist the Auditor-General and her team with any assistance they require as the audit progresses."

Michael Easson, acting chairman of ACTEW, welcomed the audit.

"This process, we expect, will be another milestone to building trust and confidence in ACTEW's water security program,'' Mr Easson said.

"The Auditor-General is completely independent and we will be entirely transparent and co-operative in assisting with this audit.''

Dr Cooper also said planning was under way for an audit of the planned Civic-to-Gungahlin tramway.

"The project is likely to be the largest and most complex capital works project undertaken by the ACT government, with potentially significant economic, environmental and social impacts for the territory,'' she said.

"The Audit Office could examine the planning and governance processes in place to support the delivery of the Capital Metro project. This could include consideration of the quality of economic, environmental, social and other information provided to decision-makers.''