"Governance" requires borders, property rights, and a means of managing those rights. Borders can separate physical or economic space, e.g., US and Mexico or agriculture and urban. Property rights in water should clarify rights in quantity and quality, to individuals or communities. Management allows for trade and sharing as well as NOT moving rights.
Borders reduce complexity by allowing people within a border to ignore actions and events outside their borders. Good governance minimizes spillovers into neighboring regions.
The institutions for managing rights do not need data as much as reliability. It's easier to say "restart the water allocation cycle on every full moon" than "take 12.34 m3 of water on your turn."
An exact, unreliable system will cause endless problems, e.g., (1) in this post.
Institutions must evolve with practice and change. it takes practice to understand a complex water system. Governance needs to change as social priorities, technology and outside conditions change.
Solutions emerging from public participation are more likely to balance and endure.* Non-monetary, communal or social solutions can often accomplish far more than monetary solutions that are distorted by market power or corruption. An acceptable governance framework allocates private (commodity) water with price or market signals and public (social) water via political mechanisms.
Bottom Line: Good pornography doesn't distract you with misplaced actors, intrusive lighting, and bad plots. Good water governance involves the right people, avoids peripheral debates, and keeps the right bits more wet than wild.
* via Fleck:
Good policy design contributes to three key public needs: progress in problem solving that will make tomorrow’s challenges easier than today’s; representation of sufficient interests, so that the policy has a positive balance of support and is politically feasible; and empowerment of the people affected, so that they can become engaged and better able to resolve their own problems.