Abstract
This study focuses on the differential hydrologic response of individual watersheds to climate warming within the Sierra Nevada mountain region of California. We describe climate warming models for 15 west-slope Sierra Nevada watersheds in California under unimpaired conditions using WEAP21, a weekly one-dimensional rainfall-runoff model. Incremental climate warming alternatives increase air temperature uniformly by 2°, 4°, and 6°C, but leave other climatic variables unchanged from observed values. Results are analyzed for changes in mean annual flow, peak runoff timing, and duration of low flow conditions to highlight which watersheds are most resilient to climate warming within a region, and how individual watersheds may be affected by changes to runoff quantity and timing. Results are compared with current water resources development and ecosystem services in each watershed to gain insight into how regional climate warming may affect water supply, hydropower generation, and montane ecosystems. Overall, watersheds in the northern Sierra Nevada are most vulnerable to decreased mean annual flow, southern-central watersheds are most susceptible to runoff timing changes, and the central portion of the range is most affected by longer periods with low flow conditions. Modeling results suggest the American and Mokelumne Rivers are most vulnerable to all three metrics, and the Kern River is the most resilient, in part from the high elevations of the watershed. Our research seeks to bridge information gaps between climate change modeling and regional management planning, helping to incorporate climate change into the development of regional adaptation strategies for Sierra Nevada watersheds.
Highlights
General circulation models (GCMs) predict an increase in air temperature across California’s Sierra Nevada mountain range, predictions vary whether the region can expect more or less precipitation [1,2]
Each 2uC increase in air temperature led to a total reduction of nearly 700 mcm of the mean annual flow for the Sierra Nevada region
It has been well documented that climate change is likely to increase air temperature and reduce snowpack in California’s Sierra Nevada [1,5,28], few studies have examined the differential impacts of climate warming for neighboring watersheds
Summary
General circulation models (GCMs) predict an increase in air temperature across California’s Sierra Nevada mountain range, predictions vary whether the region can expect more or less precipitation [1,2]. Most studies agree that decreases in mean annual flow, reduced snowpack, and more rapid snowmelt runoff are expected [3,4,5,6]. It is not well understood whether individual watersheds within a single region will respond differently to climate warming, how characteristics of the individual watersheds may temper future impacts, and how differential impacts relate to existing demands such as water storage capacity, hydropower generation, and ecosystem services. We use results from a climate-forced rainfall-runoff model to explicitly simulate intra-basin hydrologic dynamics and understand localized sensitivity to climate warming. Insights presented here are intended to help guide local adaptation strategies by highlighting regional and basin-specific trends in the quantity and timing of water resources under regional climate warming, and to illustrate which basins are the most intrinsically vulnerable to climate warming
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