Surface and groundwater relationship in an anthropically modified area

This study assessed the relationship between the recharge of the unconfined sedimentary Adamantina Aquifer and its discharge into the Batalha River in a small basin of 125 km2 that drains the municipalities of Bauru, Agudos and Piratininga (SP, Brazil). According to the Eckhardt Flow Separation Filters and Soil Moisture Accounting Procedure methods, the recharge was 312.6 mm/yr and 232.0 mm/yr, respectively; and 286.2 mm/yr to the modified-Thornthwaite method for the 2000-2018 period. Recharge values prone to converge as more extended periods are analyzed (ideally 18 years) because the sensitivities to a specific parameter tend to be mitigated over time. With the integration of the methods, we established how changes in land-use impact the aquifer recharge and, thus, the discharges and the behavior of the river's recession curve. Areas used to cultivate sugar cane (193 mm/yr), eucalyptus (150 mm/yr), or to urbanization (72 mm/yr) exert control over aquifer recharge even more than topography or type of soil. The combined and integrated use of three simple techniques allows them to be used for land-use planning and assessment of water availability in small hydrographic basins when hydrological data are scarce.