Water scarcity in arid and semi-arid regions is a great economic, environmental and social problem, where the people living in these regions have to use technologies, such as cistern, to ensure water for their survival. Given the difficulties in these regions, this paper aims to propose a methodology to estimate per capita water use for different levels of water shortage risk, ensuring water supply under the conditions of arid and semi-arid regions; and present a case study for the Brazilian semi-arid region. The methodology is based on analysis of spatial and temporal risks of water shortage in the cisterns. Analysis of the temporal risk of water shortage is based on the premise that the cistern is without water for 3 consecutive days with return periods of 5, 10 and 20 years. To ascertain the spatial risk of per capita water use associated with these return periods in hydrologically homogeneous regions, we evaluate the confidence interval associated with the average monthly water use. Thus, the proposed methodology allows to determine the potential water use in each homogeneous region. For the Brazilian semiarid region it is possible to identify the areas where local population has a greater restriction on the access to water (central semiarid region) and areas where there is greater water availability (north and south of the semi-arid). This variation of water availability allows to adapt management measures accounting for the ground conditions of each location, in order to meet the water needs of the local population.