Hydrologic Modeling on a National Scale

Abstract:

The U.S. Geological Survey has developed a National Hydrologic Model (NHM) to support coordinated, comprehensive, and consistent hydrologic model development and application of hydrologic simulations on the scale of the continental United States. The NHM provides accurate and consistent estimates of total water availability, changes in the timing and sources of flow, and measures of the uncertainty of these estimates. These hydrologic elements are essential in assessing the response of the Nation’s watersheds and ecosystems to climate and land use changes at local, regional, and national scales.

The NHM structure includes (1) a consistent geospatial fabric for modeling; (2) daily and monthly time-step models (e.g. the Precipitation Runoff-Modeling System and the Monthly Water Balance Model); (3) the ability to subset and aggregate models (nested models); and (4) multi-basin, multi-step, multi-objective model calibration procedures. In addition, continental scale applications require consistency across datasets measured with large-scale networks (e.g. streamflow and climate) and remotely-sensed products. Methods for parameter estimation, uncertainty quantification and calibration approaches also are being investigated at the continental scale with the NHM.