Explaining spatial variability in mean annual runoff in the conterminous United States

Abstract

The hydrologic concepts needed in a water-balance model to estimate the spatial variation in mean annual runoff for the 344 climate divisions in the conterminous United States (U.S.) were determined. The concepts that were evaluated were the climatic supply of water (precipitation), climatic demand for water (potential evapotranspiration), seasonality in supply and demand, and soilmoisture-storage capacity. Most (91%) of the spatial variability in mean annual runoff for the climate divisions in the conterminous U.S. was explained by the spatial variability of mean annual precipitation minus mean annual potential evapotranspiration. When soil-moisture-storage capacity and seasonality in supply and demand were added to the water balance, the explained variance in mean annual runoff increased slightly, and the error in estimated mean annual runoff decreased significantly. Adding soilmoisture-storage capacity and seasonality in supply and demand provided the most improvement in areas where seasonal supply and demand are out of phase.

Validation of Simulated Runoff From Six Terrestrial Ecosystem Models: Results From Vemap

“…For these reasons, we used mean annual HCDN streamflow (in millimeters per year to eliminate a watershed size bias) as a proxy for wetness or dryness of a watershed. Streamflow tends to be highly correlated with watershed precipitation (Dolph and Marks 1992, Wolock and McCabe 1999, Lewis et al 2000. Table 1 footnote.…”

“…(3) The Nash-Sutcliffe coefficient of efficiency (NS; Nash and Sutcliffe 1970) is another widely used statistic for evaluating the performance of hydrologic models (e.g., Wilcox et al 1990, Wolock and McCabe 1999, Peel et al 2001, Sauquet and Leblois 2001. As the ratio of the mean square error to the variance in the measured data, subtracted from unity, it is computed as…”

“…where S and Ō are mean simulated and mean observed values, respectively, as derived from the entire monthly data set (Watterson et al 1999, Wolock andMcCabe 1999). (3) The Nash-Sutcliffe coefficient of efficiency (NS; Nash and Sutcliffe 1970) is another widely used statistic for evaluating the performance of hydrologic models (e.g., Wilcox et al 1990, Wolock and McCabe 1999, Peel et al 2001, Sauquet and Leblois 2001.…”

Climate change impacts on U.S. Coastal and Marine Ecosystems

“…In contrast to the general agreement among GCMs for direction, if not the pace, of temperature change, regional projections of precipitation vary considerable (NAST 2001). Simple water-balance models developed by Wolock and McCabe (1999) based on the precipitation and temperature projections of the Canadian and Hadley models provide some basis to forecast river runoff (Fig. 1).…”

Analysis of catchment evapotranspiration at different scales using bottom-up and top-down approaches

“…Budyko (1974) proposed a semi-empirical relationship between the ratio of annual evapotranspiration to annual precipitation and the ratio of annual precipitation to annual net radiation. Considerable research has been performed on the www.intechopen.com Budyko curve (Fu, 1981;Milly, 1994;Choudhury, 1999;Wolock and McCabe, 1999;Zhang et al, 2004, Yang et al, 2008a through analyzing the interactions between climate, soils and vegetation in producing annual water balance. A simple water-energy balance equation (Yang et al, 2006 and based on the Budyko hypothesis (1974) has been used for predicting the long-term average evapotranspiration and the inter-annual variability of evapotranspiration.…”