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

Abstract

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 São 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 Tietê, Turvo/Grande, and Pardo basins, and low availability in the Upper Tietê, 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.