Geochemical and isotopic tracers integrate and trace processes across spatial and temporal scales and thus are flexible for addressing diverse questions about disturbances at local scales, or when services to stakeholders emerge at much larger scales (i.e., the river system or basin aquifer). We will integrate tracer methods with geophysical imaging, surface flux measurements, and modeling using newly acquired instrumentation capable of measuring stable isotope ratios in water and chemical constituents in situ with high frequency. We can test predictions about water pathways and ask how surface and subsurface heterogeneity and structure controls the fate and speed of water through the landscape. Our goal is to develop capabilities using tracer methods that will: (1) elucidate pathways of water movement by following the fate of precipitated water through losses above, below ground and into groundwater and runoff; (2) measure water residence and transit times across multiple scales; and (3) quantify transport and transformation of dissolved organic and inorganic compounds through watersheds and in aquifer and river systems.
The new generation of optical instruments acquired through WyCEHG will monitor, in real time, the stable isotope composition of water vapor as it is exchanged between the land-surface and atmosphere and record the dynamics of runoff and mixing in streams during snowmelt and following rainfall or irrigation events. Measurements from these experiments will be used to deconvolve the origin of water fluxes in evapotranspiration and stream flow and elucidate the pattern of surface and subsurface water interactions and recharge from precipitation. The results will uncover connections between surface water, sub-surface flow and recharge, and estimate the rate water moves through these pathways. In an experimental framework, deuterium labeling and electrical resistance tomography, coupled with release of ionic tracers, will verify transit times predicted from modeling and more conventional observations.