Abacus to Predict Groundwater Recharge at Non-Instrumented Hydrographic Basins

Abstract

One of the first steps to implement a policy for groundwater resources management is knowing the groundwater recharge. However, the unavailability of data and resources to execute field studies increase the uncertainty associated with the estimation of groundwater recharge. To fill this gap, the present work aimed to propose a method to predict groundwater recharge at non-instrumented hydrographic basins. The approach proposed is based on using an abacus to execute the transposition and/or regionalization of results generated in an experimental basin. The methodology comprised the estimation and mapping of recharge rates in the experimental basin using three distinct approaches—numerical modelling of the saturated zone, distributed hydrological modelling of the vadose zone, and the method of fluctuation of the water table elevation—and the following generation of the abacus, with average recharge values for combinations of soil class, land use/cover and slope using geographic information systems. The results indicate that the abacus is consistent for some Ferrasol areas, that the reliability of average regionalized values depends on the complexity of the physical environment—soil class, land use/cover, and slope—and that new studies, focusing on the hydro-physical characterization of soils, might produce more reliable estimations.

Groundwater Recharge in the Cerrado Biome, Brazil—A Multi-Method Study at Experimental Watershed Scale

“…Recharge spatial distribution was considered reasonable and in agreement with Salles et al [18], according to whom recharge is favored in sites with highly permeable soils, such as Ferralsols, in densely vegetated fields, and low slopes. For those environmental conditions, the recharge rates simulated by SWAT hydrological model are at similar levels [86].…”

“…The 25% estimated in Santos [85] for the same study area was considered more reasonable; • the level of uncertainty for the estimated recharge rates was not measured but was considered high due to uncertainties in the conceptual models of the methods, the uncertainties of the parameters/data, and the limitations of the results; • in terms of the spatial distribution, the potential recharge map generated by hydrological modeling was considered consistent for combinations between Ferralsols and Cerrado vegetation cover in flatter areas. For the steepest areas with Cambisols, the consistency of the map should be verified by applying another method because, according to Santos [86], the result differs greatly from that obtained by applying SWAT under the same conditions; • for effective recharge, the spatial distribution generated by numerical modeling was considered more consistent than the map generated by interpolation of the point estimates of the WTE method. However, the prior imposition of recharge zones generated by the method limits and makes the calibration process difficult.…”