Assessing Climate Change Impacts on Water Supply Reliability for Santa Clara County, California

Future climate conditions will likely not resemble historic conditions, creating long-term planning challenges for agencies responsible for water supply and flood control. To help facilitate long-term water resource planning, we compiled climate change projections for the Santa Clara Valley in California. By using an ensemble of 10 climate models, we capture some of the uncertainty in future projections and assess changes in precipitation, temperature, and surface runoff for the 2025-2054 period. We use the surface runoff estimates to calculate inflows to local reservoirs that serve as an important component of the regional water supply system. We find model consensus for wetter winter conditions, which drives increases in wet year reservoir inflows. Changes in dry year inflows show insignificant changes with the future projections, at least for the early-to-mid 21st century examined here.