Estudo hidrogeológico de um aquífero aluvial com barragens submersas na região de Santa Luzia, Paraíba.

Abstract

The shallow alluvial aquifers in the semi-arid region of Northeast Brazil could be an alternative source of water for agriculture in the region. However, research for exploration and proper management is still scarce. A pilot aquifer was investigated near the city of Santas Luzia, Paraíba, with approximately 5 km in length, ranging from 40 m to 250 m and thicknesses from 1 m to 10 m. In three existing Amazonian wells, four piezometers and a pluviometer installed in the study area, weekly measurements of the variation in water levels and the precipitation rate were carried out during 1988 and 89. Flow measurements, downstream of the B1 submerged dam , existing at the exit of the pilot aquifer, were made during the dry months. In order to map the aquifer margins, several transversal geoelectric profiles were performed. An extensive longitudinal profile revealed two more submerged dams and the morphology of the crystalline basement along the stream bed. Some vertical electrical soundings were carried out that allowed the determination of the depth until the crystalline basement. A pumping test performed in the study area, provided the hydrodynamic parameters representative for this type of aquifer. All of this field data served as input data for a numerical modeling, using the Finite Differences technique, to simulate the spatial and temporal hydrological behavior, assuming a simple model of uni-dimensional and non-stationary flow in the isotropic and heterogeneous environment. The results obtained through this simple model satisfactorily reproduce the data observed in the field. The methodology used allows future hydrogeological investigations of relatively low and short-term costs for other shallow aquifers, typical of the Northeast.