Guarani Aquifer System exploitation in Araraquara

Abstract

Araraquara is one of the many urban centers in the State of São Paulo that are supplied by the Guarani Aquifer System. This city has more than 245 production wells that exploit over 70,500 m³/d. Only 12 of these wells represent 50% of the total yield and are operated by the public water supply company. The objective of this paper was to characterize the potentiality of the Guarani Aquifer System in the area, by assessing both exploitation and hydraulic head evolution over time. Specific pumping tests have shown that the Guarani Aquifer System has an excellent transmissivity (T = 120 to 333 m²/d), with average flow rates of 108 m³/h and specific capacity from 0.1 to 13 m³/h/m. The historic water levels (maps for 1972 to 1983, 1985 to 1995 and 1996 to 2003) demonstrated the evolution of the drawdown. In the city center, the average drawdown is 10 to 15 m, which shows that the hydraulic interferences are still within a reasonable and manageable range. An assessment of the interferences between wells was also carried out, and showed that a well pumping at a rate of 200 m³/h would produce a drawdown of 32 and 21 m at distances of 100 and 1,000 m, respectively. From this situation, it is possible to conclude that the exploitation over a 30-year period does not point to an overexploitation problem.