Between 2003-2005, the Integrated and Dynamic Water Balance was made in El Salvador, specifically in the quantification of superficial water resources component. Having in mind the necessity to update it permanently was developed the systematization of the calculation processes, and several scenarios of land use, climatic variations and variations in demand were included. Subsequently, the system of the calculation of the demand of the different types from consumption and the component of estimation of underground water charge were included. As a final result, the system determines the Index of Shortage at river basin level, which relates the total demand to the water availability, for any period (Au) - en
