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Hydroscience

Our focus is on providing an accurate description of the links between water, energy, and biogeochemical cycles and atmospheric, ground, and vegetation states to advance the predictability of transient hydrologic processes leading to extreme events (e.g. droughts and flooding). We use an extensive set of tools from in-situ eddy covariance and weather stations, reflectometry soil moisture stations (both continuous and grid spatially distributed), infiltrometers, tensiometers, flowmeters, vegetation sap-flow sensors, field lysimeters, and others combined with remotely-sensed imagery from radars, radiometers, multi-spectral and thermal cameras for terrain and atmospheric property measurements. We combine all this field capacity with a digital infrastructure consisting of software and hardware capable of conducting telemetric missions and post-process data with celerity. Our team has extensive computation capability at ³ÉÈËÍ·Ìõ supercomputer center and 3D printing for sensor design, mounting, and deployment. 

 Some sub-research topics within this realm are: 

1. Surface and Root-Zone Soil Moisture and Links with Life Processes, Droughts, and Floods:  We seek to understand the processes that control the Spatio-temporal variability and predictability of soil moisture across the globe and the atmospheric, climatic, vegetative and material characteristics and mechanisms that are intrinsically linked to its variability. Our team is conducting multi-sensor observations of surface and root-zone soil moisture from continental to pixel-size distribution array. We account for profiling Delta-T and Campbell Sci soil profiling sensors and a miniaturized dual-polarization L-Band radiometer on board of a copter and process-based, hyper-resolution modeling for multiple-source comparison of estimations.     
2.  Surface Energy Budget, Evapotranspiration, and Decarbonization: We investigate the partitioning of the surface available energy from the global to the plot scales in rural and urban environments and under climate and land cover change conditions. We use a multi-physics model approach that accounts for precipitation (including snow), atmospheric forcing, vegetation cover, type and activity, soil texture and depth, soil moisture storage, and re-distribution, vadose zone energy and water fluxes, vegetation interception and shading, albedo and remote effects on energy sheltering, canopy cover and light extinction, atmospheric and stomatal resistance, soil infiltration and runoff generation mechanisms and all relevant processes at the element scale (e.g. 1 m) to be able to provide estimations of the soil surface and root-zone soil moisture and temperature, sensible heat flux, ground heat flux, latent heat flux. With the help of in-situ eddy correlation, sap flow, and lysimeters stations we provide an accurate description of vegetation processes including transpiration, net, and gross ecosystem productivity, and carbon flows. Information links from multiple observations and modeling outputs are analyzed with machine learning tools.    
3. Water Resources under Climate Change: Our team seeks to understand and improve our predictions of water stocks and fluxes under an ever-changing environment. We focus on the combination of general circulation models (GCM) under a variety of representative concentration pathways (RCP) with distributed hydrologic and social modeling to understand the complex interactions and drivers of future availability or unavailability of water in different regions of the world. The modeling effort involves water reservoirs and dam operation strategies as well as societal attitudes to water conservation within an optimization framework strategy. 
4. Flood Forecasting: The mechanisms that produce floods and flash-floods in flat and complex terrain are studied and understood from a mechanistic perspective to be able to find causality and improve predictability. Precipitation from satellite and radar forecasting models are blended with physics-based, distributed high resolution modeling to understand the ways water distributes and triggers enhanced runoff mechanisms in different terrain and vegetation coverage types. Super-computing and cutting-edge visualization tools are used to provide the best picture of the causal factors and limits of predictability. 
5. Post-fire Hydrology: Wildfires are the new normal in the U.S and the world, in part due to climate change. Through this line of work, we are unveiling the processes that rule watersheds’ response to storm events under new soil and vegetation conditions after wildfires. Since short and longwave surface energy and water fluxes change after the fire, a new, very transient hydrologic condition develops. The new condition is highly unpredictable by the previously-calibrated or steady-state hydrologic models that remiss the changes in terrain and canopy cover. We work to understand the links between fire intensity and coverage from remote sensing and observable macro and microscopic soil and vegetation properties that affect flows of water and soil. The end goal is to develop adequate prediction tools that adapt to the changes triggered by a fire in their boundary and initial conditions. 

6. Full-Scale laboratory model of sandbars, slope stability, and mass failures: We study erosion of river sandbars that examines the impact of dam operation criteria on the bank slope stability leading to mass failure through seepage. This research work is developed by means of a full-scale laboratory experiment and simulates the sandbar beaches of the Lower Colorado River Basin in Marble and Grand Canyons. These bars are considered an important resource for this riverine ecosystem that provides habitat for native fish species, a substrate for riparian vegetation, an aeolian source of fine sediment which preserves archaeological sites and campsites for river rafters. Findings reveal that there is not a significant correlation between diurnal stage fluctuation caused by the Glen Dam operation criteria and slope stability. The erosion of sandbars with a slope greater than the equilibrium slope is inevitable and after the bars reach the equilibrium slope, mass failure and seepage erosion cease. These findings are essential for decision-makers and scientists to restrict the Glen Canyon Dam operation rule.