Monitoramento da depleção e detecção dos limites de exploração do Sistema Aqüifero Guarani em Ivoti (RS): uma aplicação de geoprocessamento no gerenciamento municipal do uso sustentável de recursos hidrícos subterrâneos

Abstract

Lacking of water, as customary phenomena during the long droughts in southern Brazil, has revealed the vulnerability of public supplying systems, which are exclusively based on superficial water resources. Concerning this context, the strategic importance of groundwater has been highlighted, mainly due the exploration of SAG - Guarany Aquifer System, which rises up as a promising alternative of public supplying in large areas of Brazil. Despite the suitable aspects, the insufficient knowledge about geologic characteristics and hydrogeologic behaviour, as well as the increasingly interference of new pumping wells, could turn out to be unsustainable at mid or long term the aquifer system exploration. The Ivoti County, which uses exclusively groundwater from the Guarani Aqüífer System as public supplying resource, has expanded continuously its groundwater pumping system over the last 30 years. Continuous drilling of new pumping wells, aiming to increase the total water withdraw, was carried out following the population rising and public demand. It was done without any control, unknowing the impacts on groundwater storage and its limits of exploration. The operational break-down of pumping wells and the decreasing rates of the supplying system productivity, has lead administrators to realize that is necessary an establishment of some sustainability indicators, which allows the monitoring and use management of groundwater reserves. In this way, by using geoprocessing techniques, historical series of hydrogeological data were analyzed within the period 1973-2003, allowing an evaluation of multitemporal variations of the groundwater potential surface. The results are pointing a disequilibrium between the exploration rates and the natural recharge, with a decreasing groundwater withdraw, local static levels till 53m lowering and a general depletion of the aquifer reserves. Based on these results, it was characterized a non-sustainable exploration state of the SAG for public supplying purposes in the Ivoti (RS region).

Key words: Guarany Aquifer System, sustainable use, geoprocessing.