A Generalized Mediterranean Annual Water Yield Model:Grunsky´s Equation and Long-term Average Temperature

Abstract

To estimate mean annual water yield on ungauged watersheds, regional regression equations have been developed that are a function of upstream area, precipitation, and temperature, and are commonly used. In this study, the 100-year old Grunsky equation is used as the foundation for a fully implemented generalized Mediterranean water yield model that is based on long-term annual precipitation and temperature. The work here (1) extends and generalizes Grunsky’s equation beyond its original conditions, (2) establishes an underlying hydro-climate generalized model for average annual Mediterranean watershed water yield and loss calculation, and (3) applies the validated model to estimate watershed water yield and predict potential water yield response to watershed temperature and precipitation. The water yield model was applied to watersheds in coastal California, southern France, and Portugal, but might be applied to other Mediterranean sites for which precipitation and temperature data are available. It also can be used to examine the spatial and temporal variability for water yield and predict the effects of long-term climate changes at the regional scale.