Groundwater recharge in phreatic aquifers, a case study: modeling unsaturated zone and recharge rates of the Rio Claro Aquifer using Hydrus-1D

Abstract

The hydrological process in which water infiltrates from the soil surface to the top of saturated zone of an aquifer is called groundwater recharge. A better understanding of this process is one of the keys for a proper management of an aquifer system, especially in places where water supply relies solely on groundwater. This study presents the applicability of the one-dimensional mathematical model HYDRUS-1D® to simulate the unsaturated zone of the Rio Claro Aquifer, southeastern Brazil, in order to interpret the behavior of the aquifer recharge over time and under different rainfall regimes. Deriving out of simulations, the influence of different precipitation rates, as well as the effect of different land use on the recharge zones was assessed. Results enabled us to observe the variation of distinct properties of the soil profile, such as the spatio-temporal changes in hydraulic conductivity and soil moisture content at different soil horizons and depths due to flow and rainfall dynamics. Moreover, the average infiltration time from the soil surface to the top of saturated zone was estimated to be between 85-90 days. The precipitation/recharge ratio was at 20-30% intervals, presenting higher values in periods of greater precipitation. Likewise, changes in land use such as the increase in paved areas led to a nearly virtual zero recharge emphasizing the importance of uncovered areas for natural aquifer recharge processes.