The study aims at optimizing the water allocation in the Zarqa River Basin (ZRB) through maximizing the net value added by considering the climate change scenarios developed by the team of the study. The current water allocation suffers from unmet demands. In the future;; more wastewater will be produced and more treated wastewater is expected to be used due to the increasing population and the increased connection rate and rehabilitation and expansion of the existing treatment plants;; allocating more treated wastewater for the irrigation sector would save the fresh water sources for the municipal sector. Currently the irrigation sector suffers high amounts of losses. An improvement in efficiency would contribute in saving more fresh water too. Volume One is a Water Resources Study and Volume Two is a Socio - economical Study.