Groundwater quality assessment in Harrat Khaybar, western Saudi Arabia

Abstract Evaluating the suitability of groundwater for human use is essential for water supply and health in arid and semi-arid regions. In this work, a total of 68 groundwater samples were collected from Harrat Khaybar, western Saudi Arabia to evaluate the suitability of groundwater for drinking and irrigation purposes and to document the controlling mechanisms using pollution indices and multivariate statistical methods. The results showed that the average values of the ions Cl–, SO42–, HCO3–, NO3–, Na+, Ca2+, Mg2+, and total dissolved solids (TDS) were greater than the permissible limit for drinking water while the average values of heavy metals (HMs) were less than the permissible limit, with exceeding limits of Cr, Se, As, Zn, and Pb in some individual samples. Piper diagram indicated that 47.10% of the water samples are of Na-K-SO4-Cl type, 23.51% of Ca-Mg-CO3-HCO3 type, 23.51% of Ca-Mg-SO4-Cl type, and 5.88% of Na-K-CO3-HCO3 type. Based on the groundwater quality index (GWQI), 29 of the groundwater samples were categorized as excellent and good water for drinking purposes, while 29 samples fell under poor, very poor water, and unsuitable for drinking. Additionally, results of heavy metal pollution index (HPI) indicated that all water samples fell within the low pollution category, while the metal index (MI) results indicated that 35 samples fell within very pure, pure, and slightly affected categories, while 33 samples fell in the moderately, strongly, and seriously affected categories. Results of electrical conductivity (EC), sodium adsorption ratio (SAR), sodium percentage (%Na), Kelly’s ratio (KR), and magnesium ratio (MR) revealed that 33.82–98.5 % of the water samples are suitable for irrigation depending on the parameter type. Ions exchange reactions and dissolution of carbonates, evaporites, and silicates, as well as industrial and domestic effluents and intensive use of fertilizers and pesticides were the natural and athropogenic factors controlling the groundwater geochemistry in the study area and HM pollution in some wells.