General circulation models (GCMs) predict certain changes in the amounts and distribution of precipitation, but the conversion of these predictions of impacts on water resources presents novel problems in hydrologic modeling, particularly with regard to the scale of the processes involved. Therefore improved, distributed GCMs are required. New remote sensing technologies provide the necessary spatially distributed data. However, there are many attendant problems with the translation of remotely sensed signals into hydrologically relevant information. This book elucidates how to improve the representation of land surface hydrologic processes in GCMs and in regional and global scale climate studies. It is divided into five sections: Models and Data; Precipitation; Soil Moisture; Evapotranspiration; Runoff.