This Major Research Instrumentation (MRI) Program grant supports development and deployment of a prototype instrument cluster to make comprehensive water balance measurements in a snow pack dominated hydrologic system in the southern Sierra Nevada mountains. The central instruments will be an eddy-covariance tower (ECT) for measuring water and carbon exchange with the atmosphere. The ECT allows for estimation of evapotranspiration, a generally very poorly constrained component in water balance flux estimates. The ECT will serve as the measurement and communications hub of the instrument cluster which will also include a network of micrometeorological measurements and an embedded sensor network to capture the spatial variability of snow depth, soil moisture, air temperature, soil temperature, relative humidity and solar radiation. The cluster will be distributed in an few square kilometer area proximal to the ECT and located at Wolverton, in Sequoia National Park. The cluster will complement an existing array of hydrologic instrumentation. Quantitative information on the Southern Sierra water cycle is currently provided by only a few operational precipitation, snowpack-storage and stream-gauging stations, and by limited, intensive research networks in selected headwater basins. Evapotranspiration, soil moisture and groundwater recharge/discharge are not measured and the spatial properties of energy-balance variables driving the mountain hydrologic cycle are poorly measured across the region. The planned hydrologic instrument cluster will facilitate a more comprehensive and quantitative understanding of the water cycle and has first order impact for a range of research in hydrology, biogeochemistry, ecosystem science, and water resources. Dense spatial and temporal and network observations will support the development of advanced hydrologic models with the potential to make quantitative hydrologic forecasts, probe system response to climate and land-cover perturbations, increase understanding of basin-scale water cycles and provide defensible scenarios for infrastructure planning. The Sierra Nevada mountains are the source of 40% of the water runoff that supplies the state of California's annual needs for agriculture, industry and human consumption. An improved quantitative understanding of the dynamics and water mass balance for this system is useful for fundamental research in hydrology as well for water resources management. The network will provide a prototype hydrologic observatory that will assist in the design of future larger scale efforts planned for major catchments. UC-Merced is a new campus of the UC system that has just accepted an inaugural class of a diverse body of freshman students. UC-Merced is classified as minority serving and students would be actively engaged in research that would make use of observational data collected with the proposed hydrologic network.
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