Scenarios of future california water demand through 2050: Growth and climate change

This paper describes key activities conducted by the California Department of Water Resources (DWR) to develop and quantify scenarios of future statewide water demand through 2050 as part of the California Water Plan, Update 2009. The California Water Plan, mandated by state law and updated every five years, is used to guide statewide water policy decisions. A stakeholder driven process was used to develop three narrative scenarios describing future growth: Current Trends, Slow and Strategic Growth, and Expansive Growth. These narrative scenarios express three plausible themes or storylines that highlight important uncertainties surrounding future water demands. Water demands were quantified statewide and for the ten hydrologic regions used by the California Water Plan. Across the three scenarios there is a wide potential range of future water demand depending on the specific assumptions for growth, development patterns, climate change, agricultural land use, and background conservation. Without considering climate change total statewide water annual demand by 2050 ranges from a decrease of about 2.5 million acre feet under the Slow and Strategic Growth scenario to an increase of 6 million acre-feet for the Expansive Growth scenario. All scenarios show higher water demands by 2050 when climate change is factored in. The hydrologic region based scenarios presented in this paper are an initial effort that is part of a larger strategy to conduct a robust evaluation of future demands and alternative water management strategies in light of the many uncertainties facing water managers.