GROUPING OF WATER QUALITY OF WELLS FROM A SMALL ALLUVIAL AQUIFER: A CASE STUDY OF THE FORQUILHA WATERSHED OF QUIXERAMOBIMCE/ BRAZIL

Abstract

In most arid and semi-arid areas, groundwater emerges as an important source of water for human consumption and small irrigation. In the semiarid region of the Northeast of Brazil, alluvial aquifers are presented as a water solution for small isolated communities distant from large urban centers. These aquifers have a moderate hydrogeological potential but water of excellent quality, in comparison with aquifers located in crystalline basement areas, predominant in the Brazilian Northeast. However, these alluvial aquifers are fragile and susceptible to degradation processes of its quality by human activities, climatic variations, or hydrogeological
changes. A database consisting of 14 water samples of with hydrochemical analysis of the major ions (Ca2+, Mg2+, Na+, K+, Cl-, SO4 2- , and HCO3-) from wells distributed throughout the watershed studied, was used in the preparation of water classification diagrams. In addition, multivariate statistical analysis and reverse hydrogeochemical modeling were applied with the purpose of grouping the samples and the identification of the
main aquifer recharge mechanisms in a non-rainy season. Satellite images (LandSat 5) were used for delimiting the watershed and alluvial aquifer. The results were interpolated generating maps of similarities of quality levels for human consumption and irrigation.

Key Words: multivariate statistical analysis, alluvial aquifer, Forquilha watershed, Brazilian northeast, PHREEQC.