Groundwater resources in the State of Sao Paulo (Brazil): the application of indicators

Indicators, for groundwater resources, have mostly been employed to define the present status and the degradation tendency, regarding both quantity ( under- or overexploitation) and quality ( natural and anthropic contamination). This work presents the application of indicators in order to draw a picture of the groundwater resources situation in the 22 Water Resource Management Units ( WRMU) of the State of Sao Paulo. The seven Indicators ( I1 to I7) applied provide a general overview of groundwater dependence ( I1, I2), availability ( I3, I4), and quality ( I5, I6, I7). Considering public supply ( Indicator 1), one observes that 9 WRMUs show high (> 50% of the population supplied by groundwater), 6, intermediate ( 49-25%), and 7, low (< 24%) dependence on groundwater. Indicators 3 and 4 show that the resource still presents a great potential for further abstractions in most of the WRMUs, although there is evidence of overexploitation in the Upper Tiete, Turvo/Grande, and Pardo basins, and low availability in the Upper Tiete, Piracicaba/Capivari/Jundiai, and Turvo/Grande. Indicator 5 ( aquifer natural vulnerability) denotes that the WRMUs 2, 4, 8, 13, 14 and 18-22 ( part of the recharge area of Guarani Aquifer System) need more attention mainly where large contaminant loads are present. Indicator 6 shows the general excellent natural quality of groundwater, although it also denotes that 3 WRMUs need special consideration due to chromium and fluoride contamination. Indicator 7 demonstrates a close relationship between groundwater contamination occurrence and density/type of land occupation.