VARIABILIDADE ESPACIAL NO SISTEMA AQÜÍFERO GUARANI: CONTROLES ESTRUTURAIS E ESTRATIGRÁFICOS

Abstract

The Guarani Aquifer System includes six Brazilian states and smaller areas in Paraguay, Uruguayand Argentina. It consists predominantly of Mesozoic siliciclastic sediments of aeolian and fluvial origin in Brazilreferred to as the Pirambóia and Botucatu formations, in the Parana Basin. Regarding its stratigraphic compartments, theaquifer presents three main flow units that are identified and named after the genetic facies: dune, interdune and channelones. The structural compartmentation of the aquifer was defined from integration of previously publishedmorphostructural maps drawn from radar, satellite, digital elevation model, and also regional aeromagnetometric andgravimetric data. The main goal of the present study was to establish the structural and stratigraphical control of theaquifers regional hydrodynamics and hydrochemistry. From the flow units identified, the mean hydraulic conductivity ofthe aquifer was determined based on its sediments selection, granulometric and clay content. Top and bottom values ofthe hydrostratigraphic units were interpolated by using structural lineaments as break lines. Once the flow units and thestructural compartmentation of the aquifer were defined and its spatial variations known, its dynamic potential flowpatterns were identified, which revealed the strong structural influence on its hydrodynamics and hydrochemistry. Thepotential flow maps and the flow direction maps obtained may help in the delimitation of preferential recharge anddischarge areas as they depict a hydraulic conductivity zoning and the structural and stratigraphic control of the systemsinput and output.