Estimativa probabilística da recarga e sua sensibilidade à mudanças nos regimes de precipitação para o Aquífero Urucuia, Brasil.

Abstract

Groundwater recharge represents a key component of the aquifer water balance, directly influencing water resource availability, especially in regions where these resources are under intense pressure. The Urucuia Aquifer System, located in western Bahia, plays a strategic role in supporting irrigated agriculture, urban water supply, and the maintenance of ecosystems. However, the continuous expansion of irrigated agriculture, combined with land use changes and climate change, has intensified groundwater extraction, compromising aquifer recharge. In this context, this dissertation aims to estimate the recharge of the Urucuia Aquifer System in an area located within the Corrente River basin, using daily hydrometeorological data from five stations. Different soil water balance approaches were applied, including deterministic, probabilistic, and stochastic methods, over an extended observation period. The soil water balance modeling was based on the models developed by Porporato et al. (2004) and Feng et al. (2015), allowing the evaluation of climatic variables such as precipitation, evapotranspiration, and soil moisture on recharge formation. The results indicated that recharge is concentrated during the rainy season and virtually absent during the dry period. Additionally, seasonal precipitation patterns, characterized by variations in daily rainfall probability and mean precipitation intensity, significantly influence recharge formation, with higher frequency and intensity of rainfall during summer. A simple and robust empirical relationship was obtained, expressed as R ≈ P – 2, indicating that annual recharge can be estimated from the precipitation surplus above a constant average evapotranspiration threshold of approximately 2 mm/day. This approach proved more suitable than fixed-percentage precipitation methods, as it better reflects the local hydrological dynamics. Simulations show that reductions in precipitation may decrease recharge by over 30%, while soil moisture and evapotranspiration remain stable due to the high soil water storage capacity and deep rooting systems. The applied methodology proved effective in simulating recharge and supporting the management of the Urucuia Aquifer, emphasizing the need for sustainable use in the face of agricultural expansion and climate change.