Maximizing Yosemite’s Hydrologic Model, One Parameter at a Time

HydroSHEDS digital elevation model, based on the Shuttle Radar Topography Mission, for the Lower Merced and Lower Tuolumne River bases in Yosemite National Park, January 2009.

Team Location: Ames Research Center, Moffett Field, California

Evan Johnson (University of California, Los Angeles)
Aimee Teaby (California State University, Monterey Bay)
Mark Griffin (Arizona State University)
Carlos Carrillo (Santa Clara University)
Tejas Kannan (Henry M. Gunn High School, Palo Alto, California)

John Shupe (NASA Ames Research Center, Research Scientist)
Jim Roche (National Park Service, Chief Hydrologist at Yosemite National Park)
Cindy Schmidt (Bay Area Environmental Research Institute, DEVELOP Science Mentor)

Past/Other Contributors:
Andrew Nguyen (San Jose State University)
Vanessa Archambault (San Jose State University)
Jeffrey Stine (San Jose State University)


California obtains more than half of its annual water supply from the Sierra Nevada snowpack.  Yosemite National Park (YNP), located within the central Sierra Nevada Mountain Range, produces a significant amount of water for the state’s northern urban centers such as the San Francisco Bay Area.  Historic trends reveal extreme precipitation variability within the YNP geographic region.  However, precipitation and runoff can fluctuate between less than 50 percent and greater than 200 percent of climatological averages.  Such unpredictability presents a constant challenge for water managers throughout the state.  Advances in hydrological modeling are crucial to improving water-use efficiency at the local, state, and national levels.  The NASA Carnegie Ames Stanford Approach (CASA) is a global simulation model that combines multi-year satellite, climate, and other land surface databases to estimate biosphere-atmosphere exchange of energy, water, and trace gases from plants and soils.  By coupling CASA with a hydrologic routing algorithm known as Hydra, it is possible to calculate current water availability and observe hydrological trends within YNP.  The inclusion of satellite-derived inputs such as surface evapotranspiration, temperature, precipitation, land cover, and elevation enabled the creation of a valuable decision support tool for YNP’s water resource managers.  This geospatial assessment explained a standardized method which may be repeated in both national and international water-stressed regions.

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