Abstract Title: Assessment of the impacts of human and agricultural activities on groundwater quality in the densely populated Nile Delta using hydrochemical and remote sensing analyses

Abstract Submitted to: HYDROLOGY

Abstract Text:

Water quality in the densely populated Nile Delta (i.e. ~45 million people; density > 1000/km2) is vulnerable to degradation under the pressure of the interplay between anthropogenic (e.g. dam constructions, urban expansion and pollution from irrigation and industrial activities and sewage water) and natural (e.g. sea level rise and Nile Delta subsidence) processes. The hydrological connection between the Nile water and the Quaternary Nile aquifer in the Nile Delta and the nature of aquifer material (gravels and sands) result in a quick response to the contamination from domestic and industrial sewages and the excessive use of pesticides and chemical fertilizers and necessitate a frequent and comprehensive assessment of the groundwater and surface water quality. To achieve that, we use information from satellite data (e.g. Landsat 8, GeoEye and SRTM) to assess the expansion of urban and industrial settlements on the cultivated lands in the Eastern Nile Delta and collect surface and groundwater samples (24 samples) from the Nile aquifer and the surrounding irrigation canals and drains, and finally we analyze these samples for chemical and bacteriological compositions. The land-use map for the period between 1990 and 2018 shows that urbanization development increased by 413 km2 during the study period and shows random increase of industrial settlements along irrigation canal. Three hydrochemical facies of groundwater are reported including four chemically different groundwater facies, namely Na–Cl, MgHCO3 and a mixed type. The analyzed hydrochemical parameters indicate wide ranges of TDS (320 -1860 mg/l), Na+ (42.7–797 mg/l), NO3− (4 –163 mg/l), Mg (11.5 -122 mg/l) and Cl− (38.3 – 686 mg/l) suggesting complex hydrochemical processes and recharge from multiple sources. TDS, Pb, Ni, Fe, Cl, Mg and Na exceed the limit of the World Health Organizations standards for drinking and irrigation water quality in northeastern part of study area. Spatial analysis of the landuse map shows that high concentrations of Pb, cu, Zn, Fe2+, Mn2+ are most likely related to contamination from industrial sewage. Elevated nitrate concentrations beyond the permissible limit (50 mg/l) were reported near the drains and associated with high concentrations of E. Coli bacteria (up to 110/ 100ml) indicating a potential mixing between the domestic sewage and returned irrigation waters with the groundwater system. Further investigation of geostatistical modeling is required to better assess the pollution vulnerability in such settings.