Spatial and seasonal variation of water quality indices in Gomal Zam Dam and its tributaries of south Waziristan District, Pakistan

This study investigated the quality of water and its seasonal variation in the Gomal Zam Dam and tributaries, south Waziristan District, Pakistan. For this purpose, water samples were collected from the Gomal Zam Dam and its tributaries in the winter and summer seasons (n = 24 in each season). Water samples were analyzed and found within drinking water guidelines set by the World Health Organization (WHO), except turbidity. Water characteristics were evaluated for the water quality index (WQI) and sodium hazards. Based on WQI and sodium hazards, the water of Gomal Zam Dam and its tributaries were observed as good and in permissible levels for drinking and irrigation, respectively. The winter season has slightly poor water quality compared to the summer season due to higher contamination. Gibbs’s and Piper’s models showed that the water quality of Gomal Zam Dam and its tributaries was mainly characterized by the weathering of bedrocks. The studied water is classified as Na-Cl type and Mg-HCO3 types in the summer and winter seasons, respectively. Statistical analyses revealed that geogenic sources of rock weathering are the dominant factor for controlling the water quality of the area.