Da recarga não gerenciada à recarga gerenciada: estratégia para aquífero aluvial no semiárido brasileiro.

Abstract

Great amount of scarce water resources from Brazilian semiarid are stored at alluvial aquifers, serving as important source to supply rural communities and small irrigation, due to its intermittent rivers. Despite the importance of this aquifers, wastewater, treated or not, is disposed at dry riverbed, generating an un-managed aquifer recharge that can lead to negative impacts, demanding creation of strategy searching for correct management of this system. One option is to manage recharge this aquifers, taking advantage of hydric works, made by dams, in conjunction with treated wastewater. To formulate this strategy, a site that possess representative characteristics of the region was chosen, in which lithologic data and of water quality and hydraulic heads were monitored, as their relationship with precipitation. Therefore, the system made by Sucuru River, Sumé Dam and wastewater produced by the city of Sumé, in the State of Paraíba, were studied. It was observed that chloride concentration, used as a tracer to indicate wastewater presence due to lack of sanitation, kept high at the urban zone. However, its values and variation with time decrease along the aquifer. Seeking to understand the effectivity of soil-aquifer treatment, the presence of nutrients and bacteriological indicator were compered between the well with highest amount of chloride and the effluent of the wastewater treatment plant and better results were found for the passage of wastewater through the soil than the system composed by stabilization lagoons. Despite this apparent capacity of treatment from the aquifer, it cannot remove chloride, demonstrating the need to use water with less concentration of this parameter in order to secure its uses and avoid salinization hazard. In face of that, the proposed strategy was divided in four measures, two utilizing wastewater and two superficial water resources available and they consider financial and operational challenges that may occur, in order to promote: (i) water reuse, (ii) reduce evaporation losses and, consequently, (iii) increase offer. This proposal to promote integrated management of existing water resources will act to achieve millennium development goals.