Abstract
ABSTRACT Easily exploitable aquifers are formed along river beds in the Brazilian semi-arid region and present characteristics that enable the construction of underground dams. The estimate of the potential effective exploitation of these aquifers must take into account the pumping limits of the wells, the upstream groundwater inflows and the flows to downstream reaches and through the underground dam, whose reduction influences the downstream supply. The current research presents a real case study about an aquifer reach, with underground dam and wells, which was analyzed through computational model. We simulated the groundwater flow patterns according to different exploitation scenarios and found that there should be water extraction limitations to assure the required downstream flows. The limitations can be minimized through appropriate well locations and exploitation regimes, as well as through the implementation of underground dams. The definition of these measures becomes possible through the sound use of computational simulation, but their effective implementation will depend on negotiations among users at the basin scale, so that appropriate water permits can be issued.
Highlights
The Brazilian semi-arid region is mostly located in the country’s Northeastern region, where shallow soils formed on crystalline basements prevail and present very low water accumulation and circulation capacities
Thicker sedimentary layers result from erosion and alluvial transport processes
The aquifer has six active-exploitation wells and one 33 m-long underground dam built on canvas, which is fully penetrating down to the crystalline basement, it partially dams the flow in the cross section of the aquifer (Figure 1)
Summary
The Brazilian semi-arid region is mostly located in the country’s Northeastern region, where shallow soils formed on crystalline basements prevail and present very low water accumulation and circulation capacities. Thicker sedimentary layers result from erosion and alluvial transport processes Such phenomena, locally restricted to the beds and banks of some rivers and streams, form aquifers of easy and favorable use (ALBUQUERQUE; RÊGO, 2011). Locally restricted to the beds and banks of some rivers and streams, form aquifers of easy and favorable use (ALBUQUERQUE; RÊGO, 2011) Water catchment in these aquifers, either for human supply, animal watering or irrigation purposes, is carried out through manually excavated large-diameter wells (from 1.5 to 3 meters). These wells are known in the region as “amazonas” or “cacimbão” wells, which are often lined in brick masonry. They are, as a rule, fully penetrating wells, since they cross several lithographic, sandy and boulder layers, which are interspersed by less thick, clayey or sandy-clayey layers
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