Nile and Groundwater Interaction in the Western Nile Delta, Egypt

Groundwater is the main source for domestic, industrial, and agriculture uses in most of the new reclaimed areas in the western Nile Delta region, which affects the groundwater quality. The hydrochemistry of major ions (K⁺, Na⁺, Mg²⁺, Ca²⁺, Cl⁻, SO₄ ²⁻, HCO₃ ⁻, CO₃ ²⁻) together with trace elements (Fe, Mn, Zn, Pb, Cd, Cr, Cu, Ni) has been used to constrain the hydrochemical characteristics of groundwater, western Nile Delta aquifers. The total of 108 groundwater wells, varying in depth from 27.5 to 120 m, have been examined and sampled to carry out the physico-chemical parameters and chemical compositions of the groundwater and to obtain additional information on the possible interaction with the Nile water. This chapter deals also with water quality and contamination with nutrients (NO₃ ⁻, PO₄ ²⁻, NH₄ ⁺) and trace elements (heavy metals). The groundwater is slightly alkaline with pH’s ranging from 7.11 to 8.65 with an average of 7.9. The salinity of the groundwater as a total dissolved solid (TDS) ranges from 430 mg/L (freshwater) in some parts of the Quaternary aquifer to 24,407 mg/L (saline water) in the northwestern Nile Delta with an average of 2,705 mg/L (brackish water). It increases gradually north- and westwards due to seawater intrusion and mixing with the Miocene aquifer, respectively. The freshwater is mainly concentrated in the central-eastern part, close to Rosetta branch. The chloride (Cl⁻) and sulfate (SO₄ ²⁻) ions acquire the higher concentrations of the anions, while sodium (Na⁺), calcium (Ca²⁺), and magnesium (Mg²⁺) acquire the higher concentrations of the cations. The concentrations of the major ions are higher than the maximum standard limits, according to the World Health Organization (WHO, International program on chemical safety). The nutrient content of phosphates is also higher than the maximum standard values, while nitrate is in the critical level. The maximum concentration of nutrients was mainly recorded in the old cultivated lands, indicating the contamination from irrigation water. The concentrations of the trace elements are lower than the standard limits except for iron, manganese, and nickel. The hydrochemical composition reflects the Na-HCO₃ water type for the Quaternary aquifer, indicating recent meteoric water. Another major water type (Na-Cl) is recorded in the high salinity areas of northern and western parts. According to the US Salinity Laboratory diagram, most of the groundwaters are located in the high salinity and low sodium hazard zone. The groundwater has <1.25 meq/L RSC, which is good quality and suitable for using in irrigation for all types of soils.