Development of a methodology for building empirical models of water demand for urban supply and animal use based on watershed occupancy

Abstract

The changes in water use in hydrographic basins are related to human occupation processes, which include diverse socioeconomic activities and distinct soil cover patterns. In the Brazilian context, there is an increase in demand for water in different sectors, and this increase is associated with economic development and the urbanization process. In this scenario, for effective management and adequate planning of water resources, it is essential to understand the factors that drive changes in water use. Furthermore, there is a lack of studies that investigate the interaction between changes in water use and transformations in soil cover. Therefore, this study proposes the construction of empirical mathematical models based on multiple regression to represent sectoral water demand and its relationship with annual environmental and socioeconomic data from the Paraíba do Sul River Basin, located in the Southeast region of Brazil. Initially, associations were evaluated between water withdrawal flows for urban supply and livestock use with soil cover classes and socioeconomic indicators to identify potential explanatory variables for the models. In the calibration phase, four different mathematical approaches were tested: linear, semi-logarithmic, log-log and normalized. Subsequently, these constructed models underwent a validation stage using a set of statistical metrics. The results revealed that the standardized empirical model of urban water demand was statistically significant, with urbanized areas and urban population as input variables. On the other hand, the semi-log model of livestock water demand was derived from the livestock area and the GDP of the agricultural sector. Thus, the proposed models allow estimating water demands based on changes in soil cover within a river basin, supporting the integrated management of water resources.