Suitability Assessment of Groundwater for Irrigation in Rabigh, Saudi Arabia: A Case Study of Combined Influence of Landfills and Saltwater Intrusion

Abstract

This research assessed the combined influence of permitted landfills and unlicensed dumps coupled with saltwater intrusion on the suitability of groundwater in Rabigh, Saudi Arabia for irrigation purposes. Fourteen water samples were analyzed for physiochemical parameters, major ions, and heavy metals. Quality assessment of groundwater for irrigation purposes was conducted on basis of sodium percentage (Na %), sodium adsorption ratio (SAR), magnesium hazard (MH), permeability index (PI), total hardness (TH), Kelley's ratio (KR), and soluble sodium percentage (SSP), Wilcox and the Food and Agriculture Organization of the United Nations (FAO) standard limits. Results showed that the domination of ions is in the order Na>Ca>Mg>K and Cl>SO4>HCO3 for cations and anions, respectively. Elevated concentration of Na and Cl coupled with very strong relationships between Na and Cl (r = 0.994), Na and EC (r = 0.995), and between Cl and EC (r = 0.999) indicates a strong influence of Red Sea saltwater intrusion. According to Wilcox and the FAO classifications of salinity (Electrical conductivity (EC)) in irrigation water, it can be concluded that the groundwater in the investigated area of Rabigh is undesirable for irrigation purposes. Based on the Freeze and Cherry classification of total dissolved solids (TDS), the groundwater samples fall in the brackish to saline categories. However, saline water was recognized in the majority of the samples (64%). Concerning the FAO classification, 86% of the samples can be classified in the severe restriction category. According to the categorization of irrigation water based on sodium percentage, two-thirds of the water samples can be classified in the doubtful to unsuitable categories. The very high electrical conductivity values obtained in the groundwater samples near the landfill sites are an indication of the combined effect of leachate and Red Sea saltwater intrusion. The severe restriction is associated with 65% of groundwater samples according to the FAO classification of SAR. Nearly two-thirds of the groundwater samples fall in the medium to high sodium hazard categories. According to Kelley's ratio and soluble sodium percent, the majority of the groundwater samples (86%) show that the groundwater is undesirable for irrigation purposes. The analytical results of SSP conclude that the majority of groundwater samples (86%) are undesirable for irrigated agriculture. Samples of some groundwater wells show that the concentration of some heavy metals such as Aluminum (Al), Cobalt (Co), Copper (Cu), Chromium (Cr), Nickel (Ni), Vanadium (V), and Zinc (Zn), are higher than the corresponding FAO permissible limits.