Bilateral interdependencies between water and land uses and water availability in the Rio Grande watershed

ABSTRACT

Changes in land use-occupation and water demands in Brazil have been closely monitored due to the consequences for the water-energy-food system, specifically affecting the water availability for this system. The objective of this study was to seek evidence of bilateral interdependencies between water demands, land uses and occupations, and water availability in the Rio Grande watershed. Using the Soil and Water Assessment Tool (SWAT) hydrological model, land use and occupation and water use were spatialized over 102 sub-basins in the study area, in order to estimate their impacts within the historical series of available fluviometric stations. The correlations between uses and availability of water and land use, called the water-energy-food system, were obtained through Pearson's correlation coefficient and its significance threshold. It was observed, over the last few decades, that changes in land use and occupation led to a 40% reduction in the simulated surface runoff, while water use increased by around 30 m³/s. The antagonism between pastures and sugarcane and the uses of water related to these activities, associated with the decrease in water supply, shows that crop substitution played a significant role in the variation of surface runoff in the Rio Grande basin. Potential conflicts over water use may arise, both locally and generally in the watershed, and may even affect downstream watersheds.

Keywords:
water interdependencies; water-energy-food system; soil and water assessment tool model; land use and land changes; Rio Grande basin