Hydroclimatic Predictors.pdf

The Public Interest Energy Research (PIER) Program's California Climate Change Center developed a white paper on the development and application of downscaled hydroclimatic predictor variables for use in climate vulnerability and assessment studies. The paper outlines the production of 270-meter grid-scale maps for 14 climate and derivative hydrologic variables for the State of California.

The Basin Characterization Model (BCM) was used to process hydrological variables, and three historic and three future time periods of 30 years were developed to summarize 180 years of monthly historic and future climate values. The paper presents three analyses: trends in hydrologic variables, calibration and validation of the BCM using measured discharge values from 139 streamgages, and an assessment of trends in specific hydrological variables under four future climate projections.

The results show that increases in potential evapotranspiration dominate other influences in future hydrologic cycles, driving decreasing runoff and increased climatic water deficit. This may lead to conversion of dominant vegetation types and have implications for rain-fed agriculture. The BCM permits integration with a water balance model that can be derived for landscapes and summarized by watershed, demonstrating the utility of using a process-based model with modules representing different hydrological pathways.

Key findings include:

Increased potential evapotranspiration drives decreasing runoff and increased climatic water deficit
The BCM can be integrated with a water balance model to derive landscape-scale water balances
The results have implications for rain-fed agriculture and dominant vegetation types in the study region
The use of a process-based model with modules representing different hydrological pathways is useful for climate vulnerability and assessment studies.