Water shortages in California are a growing concern given persistent drought conditions, earlier spring snowmelt, projected future climate warming, and currently mandated water use restrictions. Increases in population and land use requirements in coming decades will place additional pressure on already limited available water supplies. USGS scientists used a state-and-transition simulation model to project future changes in developed (municipal and industrial) and agricultural land use to estimate associated water use demand from 2012–2062. Under current efficiency rates, total water use was projected to increase 1.8 billion m3 (+4.1%) driven primarily by urbanization and shifts to more water intensive crops. Only if currently mandated 25% reductions in municipal water use are continuously implemented would water demand in 2062 balance to water use levels in 2012. This is the first modeling effort of its kind to examine regional water demand related to land use incorporating historical trends of both developed and agricultural land uses.
Projected land use and land cover (LULC) change for the historical period (1992–2012) and the projected period (2012–2062) in California’s Central Valley and Oak Woodlands regions under a business-as-usual scenario. The 2012 and 2062 LULC maps represent one out of 40 possible Monte Carlo iterations modeled for each time step.