This paper introduces water into the GTAP modeling framework at a river basin level. The new model: 1) distinguishes between irrigated and rainfed agriculture using different production functions; 2) takes into account heterogeneity in land quality across agro-ecological zones; 3) traces supply of water at the river basin level within each country/region; 4) fully captures competition for land among crop, livestock and forestry industries; 5) and, most importantly, offers the potential to extend the competition for managed water among agricultural and non-agricultural activities. Individuals interested in working with the GTAP-Water data base and model are referred to the following publication in the Journal of Global Economic Analysis