Estimate of Groundwater Recharge Based on Water Balance in The Unsaturated Soil Zone

Davi De Carvalho Diniz Melo,Rafael Chaves Guanabara,Edson Wendland

doi:10.1590/01000683rbcs20140740

Davi De Carvalho Diniz Melo, Rafael Chaves Guanabara + Show 1 more

Open Access

https://doi.org/10.1590/01000683rbcs20140740

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Abstract

ABSTRACT Groundwater management depends on the knowledge on recharge rates and water fluxes within aquifers. The recharge is one of the water cycle components most difficult to estimate. As a result, despite the chosen method, the estimates are subject to uncertainties that can be identified by means of comparison with other approaches. In this study, groundwater recharge estimates based on the water balance in the unsaturated zone is assessed. Firstly, the approach is evaluated by comparing the results with those of another method. Then, the estimates are used as inputs in a transient groundwater flow model in order to assess how the water table would respond to the obtained recharges rates compared to measured levels. The results suggest a good performance of the adopted approach and, despite some inherent limitations, it has advantages over other methods since the data required are easier to obtain.

Highlights

The Guarani Aquifer System (GAS) is one of the most important water sources in South America, with an estimated volume between 25,000 and 37,000 km3 (OEA, 2009)
The spatial velocity distribution confirms the consistency of the model, once regions with unrealistic drainage values or drastic direction changes were not identified (Figure 4)
Results of recharge estimated by water balance in the unsaturated soil zone were similar to the previously obtained by the WTF method

Summary

Introduction

The Guarani Aquifer System (GAS) is one of the most important water sources in South America, with an estimated volume between 25,000 and 37,000 km (OEA, 2009). The GAS area is distributed in Brazilian (736,000 km2), Argentinian (228,200 km2), Paraguayan (87,500 km2) and Uruguayan (36,200 km2) territories (Gastmans et al, 2010). GAS is essentially confined or semi-confined, with outcrop areas, where the recharge occurs, corresponding to approximately 10 % of the total area (Wendland and Rabelo, 2010). In the State of São Paulo, approximately 15 % of the 155.800 km correspond to outcrop zone. The concentration of wells is highest in this state, accounting for 90 % of the water extraction in Brazilian territory (OEA, 2009)

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Conclusion