This is a topic that I have been looking at sporadically since I completed a research project on it for a class in law school. First some background - Prop. 207, the private property rights initiative passed by Arizona voters in 2006 limited the ability of local jurisdictions to implement new regulations that would restrict development of property. When the value of property is diminished by such regulation, the property owner has a right to be compensated for that decrease in value. The important catch (for my purposes here) is that the property owner must have vested rights to develop the property in a certain way before the regulation is implemented. In the past, most developers secured water supplies for their developments after getting approvals from zoning boards, county supervisors, etc. where a change to the comprehensive plan or existing zoning was necessary. That meant the development was pretty much a done deal by the time the developer put plans in place to secure water supplies. Therefore, the development was entitled to have the necessary water regardless of what that meant for other water users.
Recent changes to land use policies in many areas have created requirements that developers submit details on the proposed water use associated with a development prior to obtaining necessary land use approvals. This allows local government to either deny approval to development that would have a deleterious impact on water supplies, or (more likely) to impose certain requirements on the developer - i.e. conservation, water use limitations, water recycling requirements. This is the sort of policy that Pima County recently included in an amendment to their comprehensive plan. Not only does this policy give the county more of a say in the type of development that occurs, where it occurs, and how much water it will use. Perhaps more importantly, it places the water supply analysis before any land use approvals, which prevents the developer from obtaining vested development rights, thereby avoiding the risk of any takings claims (pursuant to Prop. 207) against the county.
This is a very significant development in the creation of sensible land use policies that provide necessary links to water use policies that had been lacking for far too many years. And in my opinion it's more than a little ironic that the policy was likely developed (at least partially) in response to a voter initiative intended to protect the rights of private property owners and limit the ability of governments to impose limits on the ability of property owners to develop their land as they wish. For that reason alone, Prop. 207 may have been a good thing.