Hydrochemistry and thermal activity of damt region, Yemen

The aim of this study was to identify the complex hydrogeological and hydrochemistry conditions of Damt region, through determining hydrochemical properties of groundwater in the study area. According to the results of hydrochemical analyses, sampled waters can be divided into three groups: cold, thermal, and mixed waters. Thermal waters in the area are characterized by Na–HCO₃, while the cold waters by CaHCO₃ facies. HCO₃ indiscriminate cation and/or Na-indiscriminate anion are present in many places in the region and indicate generally mixing water. Only three villages with dental fluorosis observed using water elevated in F⁻ for drinking. Agricultural and liquid waste disposal are the main sources of pollution, leads to increase of Na, Cl, NO₃, Cd, and Iron. The groundwater flow is from north, northwest, and northeast to the south. Within this regional trend, structural controlling groundwater flow along Wadis and it flows from upper reaches of tributaries toward the main channel, then downward to the south of the study area. The similarity of TDS and Cl concentration at Qa’a Al Haql and Al Nadirah between aquifers indicates hydraulic continuity between alluvial and the underlying volcanic, while at Damt no hydraulic continuity found between alluvial, volcanic and Sandstone aquifers. The temporal variation shows slight decrease in the concentration of nitrate and sulfate of thermal water indicating previously high gas content of nitrogen, hydrogen sulfide in the thermal active region. The developed conceptual model of water circulation indicates flood waters infiltrate slowly through the wadi bottoms in the East where Sandstone aquifer outcrops. These waters flow westward, following the westerly dip of the Sandstone through the effects of gravity, gains heat and dissolve materials as it comes in contact with the numerous dykes, which are the feeders to the overlying volcanoes and sputter cones. All thermal water samples from Damt region fall into immature water field in NA–K–Mg diagram. Therefore, the results obtained from the cation geothermometers should be taken into account as doubtful.