Evaluation of Groundwater Quality under Agricultural Land Use in the Sub-Catchment Area of Ras El-Ain

The evaluation of groundwater quality under agricultural land use and fertilizers’ application was assessed by the physio-chemical parameters (20 parameters) of the springs of Ras El-Ain and 24 wells upstream. This study allows the investigation of chemical contamination reaching Ras El-Ain springs, an ecologically-rich site and part of Tyre Coast Nature Reserve, in addition to diverse well sites of mainly agricultural uses, located in the lower sub-catchment area of Ras El-Ain. The results of physio-chemical analyses show that their pH values are all alkaline, probably due to their rock exposure to Eocene Limestone (E); TDS and EC values are acceptable in all sites. 17 of the 26 sites are contaminated with Nitrite (${\text{NO}}_2^{？}$ ), 15 of which are wells and the other two are Ras El-Ain springs (sites 24 & 25); all contaminated sites by (${\text{NO}}_2^{？}$ ) exceed only the drinking water guideline by WHO, which entails restricted agricultural use for irrigation, and prohibiting water distribution for drinking and domestic purposes. Only sites (1) and (23) show very high Nitrate (${\text{NO}}_3^{？}$ ) content, with site (1) exceeding both limits for drinking and irrigation water guidelines set by the WHO and FAO respectively, while site (23) exceeds only the limit for drinking water. The origin of contamination with Nitrate and Nitrite is agricultural fertilizers. Sites (20) and (21) are contaminated with Fluoride (F^？), exceeding only the drinking water limit. 15 sites (excluding Ras El-Ain springs) are contaminated with Bromide (Br^？), exceeding only the drinking water limit. No other ions or heavy metals’ contamination were detected in the study sites. PCA statistical analysis shows that sites (1), (12), (20) and (22) are the most contaminated sites mainly with Nitrite, Nitrate, Fluoride and Bromide, primarily caused by over application of agrochemicals, proving the negative effect of unregulated agricultural land-use on groundwater quality.