Abstract
ABSTRACT The recent drought events and the population growth in São Paulo State (Brazil) have caused many municipalities to increase the groundwater exploitation of the Guarani Aquifer System (GAS) for the public water supply. In Bauru City/SP, the extraction of water from this Aquifer is expected to increase from 3699 m3/h (2014) to 4465 m3/h (2034). However, its long-term overexploitation may compromise the amount of available groundwater. The Analytic Element Method was used for groundwater flow modeling at steady-state, which includes the regional flow, the water withdrawal from wells and the main local geological conditions. The hydraulic gradient 0.82 m/km was estimated in the GAS in Bauru City. The potentiometric drawdown in the GAS in Bauru was estimated as 50 m since the beginning of the groundwater exploitation. The drawdown for the groundwater pumping scenario in 2014 is higher than 15 m in Piratininga and Agudos and lower than 10 m in further cities. The expected drawdown for the scenario of 2034 can reach 15 m in comparison with the scenario of 2014, in the North of Bauru City, where the future wells will be located.
Highlights
The Southeastern Region of Brazil, which has approximately 85 million inhabitants, experienced extreme events of drought in the years 2013 and 2014 (ESCOBAR, 2015), when low precipitation levels were registered
The hypotheses defined are: i) the aquifer is confined, with no recharge or discharge areas and the only groundwater input in the system is the regional flow; ii) the aquifer is homogeneous and isotropic, the hydraulic conductivity (K) is uniform; iii) the steady-state flow has been reached; iv) the aquifer is infinite; v) the only pumping wells that extract water from Guarani Aquifer System (GAS) are those drilled in Bauru City (Figure 3); vi) the aquifer in a 7 km radius circle area centered in Piratininga City is 75% thinner than the regional aquifer thickness average, according to geological information from Paula e Silva and Cavaguti (1992), Silva (2009) and C3 Consultoria (2015)
The groundwater flow of the Guarani Aquifer System was modeled by the Analytic Element Method for different scenarios at steady-state flow
Summary
The Southeastern Region of Brazil, which has approximately 85 million inhabitants, experienced extreme events of drought in the years 2013 and 2014 (ESCOBAR, 2015), when low precipitation levels were registered. GAS is the second largest aquifer in the world with 1.1 million km of occurrence area (OAS, 2009) It is a sandstone aquifer located in the southern region of South America, in Brazil, Paraguay, Argentina and Uruguay. Bauru City (Figure 1) is located in the State of São Paulo and overlies the GAS It has a population of approximately 370,000 inhabitants (IBGE, 2016), who consume water supplied by the Department of Water and Wastewater (Departamento de Água e Esgoto – DAE, in Portuguese). The increase in water exploitation causes the drawdown of potentiometric levels, which interferes with the pumping conditions of operating wells. The perforation of new wells by the Department of Water and Wastewater will be considered, according to the guidelines of the Water Master Plan of Bauru (HIDROSAN, 2014). Equipotential and drawdown maps were designed for different years and pumping rate scenarios
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