WATER TABLE FLUCTUATION METHOD TO ESTIMATE THE RECHARGE OF THE FREE AQUIFER IN THE GUARIROBA RIVER BASIN, CAMPO GRANDE – MS

The Guariroba river basin was decreed as an Environmental Protection Area (EPA), and with a surface of 360 km² it is great importance to the municipality Campo Grande because supports almost half water supply system latter. predominantly covered by Cretaceous sediments Caiuá Group, which constitutes free aquifer known Bauru Aquifer System (BAS). Recent studies have confirmed contribution BAS in maintenance base flow drainage. Therefore, quantification groundwater recharge (GWR) becomes fundamental. This work used table fluctuation (WTF) method, based on variations piezometric surface-water measurement, estimate GWR basin. From Mar 2015–Feb 2017, monthly static level were registered 13 tubular wells located EPA. Considering 1480 mm annual precipitation, estimated average 356 mm⋅year–1, varying between 210–694 mm⋅year–1. Despite considering lower value effective porosity parameter (Sy = 0.1) than one suggested for BAS, GWR-to-precipitation ratio (24%) more double that adopted state environmental agency (10%).