The Commonwealth water assets are held by the Commonwealth Environmental Water Holder, which falls under the responsibility of the Minister for the Environment and Energy. However, I understand that, under the Intergovernmental Agreement on Implementing Water Reform in the Murray Darling Basin, all basin jurisdictions agreed that:

… the characteristics of licence entitlements held for environmental water use were not enhanced or diminished relative to like entitlements held and used for other purposes.

There were a couple of other elements of the questions from the senator that I wasn't able to answer. I would be happy to arrange a further briefing on those details of this important issue.