Groundwater vulnerability and risk mapping of the Quaternary aquifer system in the Northeastern part of the Nile Delta, Egypt

Abstract

As the most valuable natural resources, protection and management of groundwater is vital for human evolution,
socio-economic development and ecological diversity. This paper presents the groundwater vulnerability mapping
of the Quaternary aquifer system in the northeastern part of Nile Delta using Weighted Multi-Criteria Decision
Support System model (WMCDSS). This model has been implemented using Geographic Information System to
delineate groundwater zones and to suggest a protection and improvement plan for major groundwater wells in the
area. Six thematic layers were digitally integrated after assigning different weights (Wf) and rates (Rf) to them. These
GIS layers have been created to adopt the most indicative criteria for investigating the groundwater degradation
trends from sea level rise and seawater intrusion. The chosen layers are: total dissolved solids (TDS), rCl/rHCO3
ratio, sodium adsorption ratio (SAR), groundwater type, hydraulic conductivity (K) and well discharge (Q). Weights
have been assigned to all these layers according to their relative importance for groundwater vulnerability, whereas
their corresponding normalized weights were obtained from their effectiveness factors. The groundwater
vulnerability map indicates four classes ranging from very low to high. According to this map, the promising
localities for groundwater usage are located in areas where very low to low vulnerability has been observed. These
localities are distributed over 4080 Km2 area, covering 53.68% of the total study area. The areas having moderate to
high groundwater vulnerability are more than 3520 Km2, indicating a deterioration of groundwater quality in 46.32%
of the study area, which need special treatment and cropping pattern before use.