Washoe County, Nevada voters convincingly approved an initiative measure that ties regional planning and growth to available water resources...
The measure requires the amendment of the Truckee Meadows Regional Plan (“TMRP”) to require future land use and water requirements in the county are in balance.
The practical impact is to have regional planners plan for 200,000 more people in the county for a total of 600,000 persons based on current water use and available water.
In theory, the measure requires county planners to create a plan for full build-out of the county. What's interesting about the measure that was approved is that the ballot initiative was only one sentence long:
"Shall the Truckee Meadows Regional Plan be amended to reflect and to include a policy or policies requiring that local government land use plans be based upon and in balance with identified and sustainable water resources available within Washoe County?
Stating it in such simple terms will create extensive work for lawyers and planning administrators in that area, working out how it should be implemented. I suspect it was stated simply in order to garner support. It could be interpreted to require something pretty similar to what is required in Arizona under the "Growing Smarter Plus Act", requiring counties and municipalities of a certain size to include a water resources element in their general plan. This is required to consider how much water is available and how much growth it can support under given conditions, but also includes a provision for demonstrating how additional sources of water may be obtained if projected growth will outstrip existing supplies.
The Washoe County initiative makes no reference to supply augmentation, merely referring to "identified and sustainable water resources" available in the county. That could be interpreted to place a pretty firm cap on future growth under one possible interpretation. Look for lots of litigation to spring from this measure in the future.
After doing some additional reading it seems that local law in Washoe County requires dedication of water supplies to the county before a new development can receive water service (this was noted in the WS article). This ensures that water supplies are available to serve new development - but says little about sustainable water supplies, that is determined by the State Engineer. However, I'm not sure what this means for developments that will be self-supplied for water service. In that case the developer would still need to find available water - either by application to appropriate available water or by purchase of existing rights. If anyone reading this knows what laws/regulations apply to developments in Nevada, or Washoe County that will be self-supplied for water I would love to hear from you.