Contribuição hidrogeológica para a protecção das zonas de Recarga do aquífero que abastece a Cidade de Xai-Xai

Abstract

Groundwater represents one of the planet's main freshwater reserves and plays a fundamental role in human supply. In Mozambique, the sustainable management of water resources is currently one of the highest priorities for the authorities that manage this precious liquid. It is estimated that most of the Mozambican population is supplied through groundwater, for this reason it becomes vital to highlight the aquifer that supplies the city of Xai-Xai, which covers an extensive area of ​​approximately 1355 km2, where the humid to dry tropical climate predominates, with gentle to steep relief and a predominance of sandy soils. The objective of this project is to contribute, hydrogeologically, to the protection of the aquifer that supplies the city of Xai-Xai. To this end, the project used recharge zones, electrical conductivity values ​​and protection zones to create maps indicating locations with different degrees of sensitivity and with differentiated management and protection approaches.

From the results obtained, it was possible to distinguish 4 main recharge zones: the high and very high recharge zones, and the moderate and low recharge zones. By simultaneously analyzing the recharge zones and the borehole distribution, it was identified that the high and very high recharge zones are located in areas with critical sanitary protection and need more attention due to the excessive exposure of those boreholes to pollutants. The spatial analysis of electrical conductivity values ​​resulted in a map divided into 4 classes, namely, good quality water with low salinity and suitable for human consumption, i.e., less than 414 µS/cm, water of moderate quality, slightly mineralized, but still acceptable for consumption (in the range of 415 to 1410 µS/cm), poor quality water, but useful for irrigation, and very poor quality water, which is not suitable for either consumption or irrigation (above 1420 µS/cm). The study area consists mainly of moderate quality, slightly mineralized water, where the water-rock interaction is reduced and consequently there is less dissolution of salts in the aquifer. Based on all the results obtained, it was possible to identify the areas of the Patrice Lumumba neighborhood, neighborhoods 6 and 9 of Chongoene, Siaia neighborhood 2, and Fidel Castro neighborhood that need protection. (TRADUÇAO NOSSA)