Abstract:

The Mio-Plio-Quaternary groundwater of Mchira-Teleghma suffers from an increasing rate of salinity especially in the northwestern part. To identify the reason for the water’s salinity and its aptitude for irrigation, physico-chemical analyses of 20 water samples, which were based on the different physical and chemical parameters (electric conductivity EC, pH, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃⁻, Cl⁻, SO₄²⁻, NO₃⁻ and Sr²⁺), were carried out during the period of October 2015. This study showed disquieting anomalies of electric conductivity that reached the value of 4376.14 µS cm⁻¹. The statistical analyses, the multivariate statistics: the principal component analysis, Q-mode cluster analyses, Sr²⁺/Ca²⁺ ratio and water type showed that the hydrochemistry of Mchira-Teleghma groundwater is controlled by the dissolution of carbonate rocks and the leaching of evaporite processes, which proved that these anomalies of the MPQ groundwater’s salinity of Mchira-Teleghma are mainly determined by the leaching of Triassic gypsum formations process. This hydrogeochemical process generates an unsuitable quality of water based on Wilcox’s and Water Quality Index’s methods, whereas Richard’s method classifies all water samples to C3S1 and C4S1 classes as they are recommended to be used with salt-tolerant species in well-drained and leached soils.

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