Plain English Summary

The seasonal water storage provided by Sierra Nevada snowpacks is central to water security for both the world’s food production and urban economies. Recent research in California’s Sierra Nevada illustrates how advances in snowpack and water-balance measurements, plus prediction of snow accumulation and melt, are central to improving forecasts of water resources in a warming climate. Estimating the value of snowpacks and how they are changing provides a baseline for evaluating investments in restoration of headwater forests that will affect snowpack storage and snowmelt runoff, and in providing replacement storage as snow becomes rain and snowpacks decline. Science communication featuring Sierra Nevada snow through written, broadcast and film media can enhance public understanding and provide a basis for infrastructure and operational investments to address water security in a changing climate.

Abstract

Snowpack- and glacier-dependent river basins are home to over 1.2 billion people, one-sixth of the world’s current population. These areas face severe challenges in a warmer climate, as declines in snow resources put more pressure on dams and groundwater. Closer to home, the seasonal snowpacks in California’s Sierra Nevada provide water storage to both sustain productive forests and support the world’s 6th largest economy. Rivers draining the Sierra supply the state’s large cities, plus agricultural areas that provide nearly half of the nation’s fruits and vegetables. Water storage is central to water security, especially given California’s hot dry summers and high interannual variability in precipitation. On average seasonal snowpacks store about half as much water as do dams on Sierra rivers; and both the magnitude and duration of snowpack storage are decreasing. Precipitation amount and snow accumulation across the mountains in any given day, month or year remain uncertain. As historical index-statistical methods for hydrologic forecasts give way to tools based on mass and energy balances distributed across the landscape, opportunities are arising to broadly implement spatial measurements of snowpack storage and the equally important regolith-water storage. Advances in applying satellite and aircraft remote sensing, plus spatially distributed wireless-sensor networks, are filling this need. These same unprecedented data are driving process understanding to improve knowledge of snow-energy-forest interactions, snowmelt estimates, and hydrologic forecasts for hydropower, water supply, and flood control. Estimating the value of snowpacks and how they are changing provides a baseline for evaluating investments in restoration of headwater forests that will affect snowmelt runoff, and in providing replacement storage as snow declines. With California facing billions of dollars of green and grey infrastructure improvements, which must be compatible with the state’s aggressive carbon-neutrality goals, it is critical to build support for expenditures. Science communication featuring Sierra Nevada snow through written, broadcast and film media can enhance public understanding and provide a basis for infrastructure and operational investments to address water security in a changing climate.

Citation

Bales, R. (2017): Making up for lost snow: lessons from a warming Sierra Nevada . Fall Meeting, American Geophysical Union, December 2017. Abstract C21H-04..