Características hidráulicas das camadas aqüíferas da Formação Guabirotuba e o potencial explotável na região da Bacia do Iraí, Curitiba-Paraná

Abstract

The main objective of this work is to determine the hydraulic characteristics of the aquifers layers of Lower Pliocene sedimentary sequences in Guabirotuba Formation and by this way evaluate the exploitable groundwater potential in the Upper Iguaçu Irai river basin. To achieve these goals the potentiometry of water stored in Guabirotuba formation was established to set the main directions of groundwater flows, characterizing the discharge areas of the aquifer. The study area is located 15km NNE from Curitiba urban area, at the vicinity of the Irai river dam. The Guabirotuba Formation consists predominantly of clays (aluminous smectites and interstratified) , and at its lower level, specifically in the study area, there are unconsolidated sands and gravels layers with a thickness ranging between 10 to 15m. In a single tube well drilled in these sediments the discharge range was of 80 m3 × h-1, its waters show precipitation of iron and manganese in the filter sections. So that the use of such water requires continuous treatment to eliminate these elements. The mathematics simulations show the contributions of Lake Irai waters to the recharge of Guabirotuba aquifers. Their flow is in the opposite direction of the groundwater flow, and also opposite to the general discharge direction of the water drainage network in this region. The granules effective porosity in arcosic sandstone is 28% in average, and the storage coefficient is about 5 × 10-4, permeability varies between 1.22 × 10-4 and 1.96 × 10-4m × s-1,the transmissivity varies from 3.6 to 7.6 m2 × h-1, the mean flow velocity ranges from 6×10-3 to 3 × 10-6m × s-1and the total exploitable discharge for a battery of 15 tube wells corresponds to 150 L ×s-1.