Evaluation of hydrogeochemical characteristics, spatial distribution of major ions, and water quality for drinking and irrigation in six districts of the Dodoma region in Tanzania.

Abstract

The present study was carried out to evaluate the hydrogeochemical characteristics, spatial distribution of major ions, and quality of water for drinking and irrigation purposes in six districts of the Dodoma region. The results show that mineralization levels exist along the gradient and are concentrated in the southern part of the region. The order of Electrical Conductivity (EC) was found to be Kongwa > Mpwapwa > Chamwino > Dodoma Urban > Kondoa > Chemba. The percentage of samples in Kongwa district that exceeded the WHO guideline was discovered to be 68.42% for EC (<2500 μS/cm), 85.90% for Ca2+ (75 mg/l),89.50% for Mg2+ (50 mg/l),89.50% for K+ (12 mg/l), 52.63% for Na+ (200 mg/l),46.67% for SO42− (250 mg/l), 94.74% for Cl− (300 mg/l) and 84.21% for HCO3−(250 mg/l). The mean value for some of the parameters in Kongwa district are; 3045.58 ± 1107.64 μS/cm for Electrical Conductivity (EC), 225.91 ± 160.52 mg/l for Ca2+, 116.09 ± 54.64 mg/l for Mg2+,11.85 ± 3.17 mg/l for K+,264.33 ± 144.04 mg/l for Na+, 278.07 ± 335.39 mg/l for SO42−, 608.93 ± 296.17 mg/l for Cl−0.295.86 ± 100.59 mg/l for HCO3−. The order of the cations and anions was found to be Na+>Ca2+>Mg2+>K+ and Cl− > HCO3− > SO4−2. The dominant hydrochemical facies was found to be a mixed Ca–Mg–Cl–SO4 type in all Dodoma districts. Wilcox diagram, Sodium Adsorption Ratio (SAR), Kellys Ratio (KR), %Na, Magnesium Absorption Ratio (MAR) indicate that most of the water in Dodoma is suitable for irrigation purposes.