The current study proposes a methodology for groundwater resource evaluation and hydrogeological exploration specifically designed for natural mineral water projects. It is applied to the recharge area of the Guarani Aquifer System, State of São Paulo / Brazil. In that area, this aquifer is represented by Botucatu (Upper Jurassic - Lower Cretaceous) and Pirambóia (Triassic) sedimentary formation. Part of the studied area is recovered by Serra Geral formation (Early Cretaceo) mainly basaltic and basaltic-andesitic litotypes. All the above-mentioned litotypes are located within the Paraná Sedimentary Basin (Cretaceous – Ordovician).
It is common sense that natural mineral waters of low mineralization are preferred by Brazilian consumers due to their specific taste. In addition, capacity high enough to supply a factory and low exposure to anthropogenic risks regarding both quality and quantity (contamination and superexploitation respectively) are also important characteristics to be considered for natural mineral water exploration purpose.
The Transnational Guarani Aquifer System is the second largest in size and capacity in the world. It is located in the South American countries of Argentina, Paraguay, Uruguay and Brazil. Its specific hydrogeological characteristics favor robust projects for the natural mineral water market (bottled water industry). In its outcropping zone, in the State of São Paulo, Brazilian territory, boreholes flow rates are in the order of 20 to 40 m³/h, with specific capacities superior to 4,0 m³/h/m. Hydrochemistry is of low to moderate mineralization, with predominating bicarbonated-magnesium and calcium-magnesium facies mainly oligomineralized as well as fluorinated. The pedological and geological context of this area, as well as flow paths in the aquifer, protect the groundwater and reduce quality risks (physico-chemical and microbiological).
The main parameters used for the hydrogeological prospecting methodology are listed below:
I) Lithology of Aquifer: Sandstones of the Pirambóia and Botucatu Formations - as reservoir
II) Hydrodynamic parameters: Specific capacity and thickness of aquifer
III) Hydroclimatological parameters: Analysis of the regional recharge
IV) Aquifer protection: pedology and presence the overlying basalts of the Serra Geral Formation
V) Hydrochemistry: Hydrochemical profile and mineralization (residence time, characterization and classification)
VI) Land Use: Risks related to interferences (quantity and quality)
VII) Economic parameters such as distance from main consummation area and main infrastructures such as highways.
Other parameters such as Slopes, Geomorphology, Drainage Density are used as complementary data.
All these parameters were input as vector data in a GIS, affected with ponderation coefficients and then crossed to draw groundwater potential maps. Various maps were issued and discussed with decision makers according to the weight they want affect to the various hydrogeological and economic parameters.
This methodology is effective and can be used in other hydrogeological contexts as far as business strategies and local specificities are considered.