The integration of isotope data and hydrological models to support sustainable water resources management

The U.S. Geological Survey (USGS) Modular Modeling System (MMS) is an integrated system of computer software that has been used to support the development, coupling, and application of hydrological and resource-management models for use in making complex, operational decisions regarding sustainable water management. Estimates of the spatial and temporal distribution of water-balance components, including surface water, ground water, and evapotranspiration, are typically made using calibrated hydrological models with few measures to validate these estimates. Knowledge of the sources and magnitudes of water-balance components is critical to sustainable water-resources management. To provide improved model estimates of the explicit partitioning of water-balance components, simulation of the isotopes (18O and 2H) has been added to selected hydrological process modules in MMS. Isotope data can be used in combination with physical data to simulate water and isotope storages and fluxes within a basin at daily, monthly, or seasonal time scales. Models were developed, tested, and evaluated using the Shingobee River Headwater Basin, Minnesota, USA. (author)