Isotope tracers in the water cycle


Water isotopes are the foundation for understanding the H and O isotopic composition of plant and animal tissues, supporting applications in areas such as ecophysiology, biogeochemistry, and migration ecology. Moreover water isotopes can record the impact of humans and the biosphere on the water cycle. The isotopic compositions of environmental waters have been extensively documented through global and national monitoring programs and thousands of published studies and reports. Long-standing theory relates variation of water isotope ratios to water cycle processes. Of primary importance is the transfer of water between liquid or solid and vapor phases during residence within or transport through a system (e.g., the atmosphere, streams, or plant tissues), which preferentially partitions the heavier isotopes 2H and 18O into the liquid and/or solid phases. In recent years, analysis of regional to continental scale datasets for precipitation and surface water isotope ratios using statistical and process-based models has demonstrated the potential to extract useful data on hydrological systems. The extension of this work to probe ecohydrological phenomena and the integration of stable isotope monitoring data with other environmental geodata has been limited, however.

This project supported postdocs who advanced the application of spatial analysis and modeling methods in isotope-based ecohydrological and hydrological research. Among the key questions addressed were:

  • Can isotopic monitoring data documenting the inputs (precipitation), outputs (streamflow) and boundary conditions (atmospheric vapor) be used to extract information on the spatial and temporal variability of catchment-scale partitioning of rainfall into runoff, evaporation, and storage?
  • Over what range of catchment scales and conditions can this be done, and to what degree does the use of model-derived data products to represent one or more isotopic parameters at large spatial scales compromise the application?
  • Can factors such as climate, land management (cropping, irrigation, urbanization), physiography, and ecosystem productivity (NDVI) be correlated with isotopic indicators for regional variation catchment water fluxes, and to what degree are these relationships static over larger (continental) scales?

Affiliated faculty

Bowen, Brooks, Dawson, Kendall, McDonnell, Pataki,Noone


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