A low-cost approach to map natural groundwater recharge potential zones of a tropical watershed with complex land occupation

Abstract

Groundwater recharge is one of the components of the water cycle and is the most difficult parameter to estimate due to multiple factors that can influence the water percolation until it reaches the water table, such as land use/cover, slope, and soil texture, besides climatic conditions. Given that groundwater is Brazil's most widely exploited natural resource and its significance in sustaining ecosystems, apart from its role in guaranteeing the city's water security, mapping zones of recharge potential is a growing demand for water resources management. This work uses the GIS approach and the water balance (2010–2019) to map the groundwater recharge potential zones of the Adamantina Aquifer in Urânia (São Paulo State, Brazil) delimited on a local scale by the Córrego Comprido watershed. The results showed that 39% of the area has a recharge potential of 165 mm/year or 13% of the average annual precipitation (APPT) for the time, reflecting the gently undulating topography (2–7% slope) with sandy soil texture and shrubby herbaceous cover. Maintaining these same terrain characteristics and changing the land use/cover only, the presence of eucalyptus trees would decrease the recharge potential by 32% (111 mm/y; 9% of average APPT). As another example, the urban occupations would cause a reduction of 80% for the same parameter (33 mm/y; 3% of average APPT). Furthermore, in urban areas, a developing recharge potential value of only 7 mm/year (1% of average APPT) corresponding to sandy lands but with slopes of 7% was observed, demonstrating the primary control of land use/cover and topography in the estimates. The predominant recharge potential value of 165 mm/y correlated with the results of previous recharge studies conducted in Urânia. It demonstrated the versatility of this approach to extrapolate over large areas when required.