Global Hydrological Archive and Analysis System (GHAAS) Water Balance Model

We assess these functions at the continental-scale using input data and validation targets distributed across the relatively data-rich conterminous United States. The model comparison results and analysis are described in Vorosmarty et al. Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modeling, Journal of Hydrology 207 1998 pp.147-169.

Water Balance Model (WBM) The water balance model used in the GHAAS (USA) application simulates soil moisture variations, evapotranspiration, and runoff on single grid cells using biophysical data sets that include climatic drivers, vegetation, and soil properties. The state variables are determined by interactions among time-varying precipitation, potential evaporation, and soil water content. The original model is described in detail in Vorosmarty et al. (1989, 1996) and Vorosmarty and Moore (1991).

For this application, the model was run to steady state using a set of climatologically-averaged datasets, described below. General Information: Spatial resolution: 0.5 x 0.5 deg., latitude x longitude grids. Temporal resolution: monthly, model estimates for a long-term-mean year.

These data represent reference data. This Collection contains 4 datasets which provide model predictions of actual evapotranspiration and runoff using two model run scenarios for rooting depth. A dataset for model prediction of potential evapotranspiration is also included as well as a dataset for model inputs.

The model inputs dataset includes the following variables: % sunshine, solar radiation (cal-cm2/day), precipitation (mm/mon), vapor pressure (kPa), wind speed (m/s), temperature (min, max, mean, range) (deg. C), root depth, elevation, soil texture, land cover, runoff (mm/yr), dewpoint temperature (deg. C).

Input data have been assembled from many sources, see Vorosmarty et al. (1998) or Data Center URL for more details.