Groundwater vulnerability assessment in different types of aquifers

The concept of groundwater vulnerability is used in groundwater management and risk assessment. Among the parameters contributing to groundwater vulnerability are: depth to groundwater; net recharge rate; aquifer media; topography; vadose zone; hydraulic conductivity; aquifer thickness; and, pumping density rate in case of over-pumping. Groundwater is considered an important water resource in Egypt. Hence, this valuable source should be evaluated against its vulnerability to all possible pollution risks. In this research, three areas are selected and representing different aquifer types with different hydrogeological characteristics. The first area is Al-Minia governorate to represent the Nile valley region, which is underlain by the Nile valley aquifer. The second area is Wadi Al-Natrun to represent the Nile Delta fringes region, which is underlain by Moghra aquifer. The last area is El Kharga Oasis to represent Western desert region, which is underlain by Nubian Sandstone aquifer. A groundwater vulnerability maps for the three regions are produced using Microsoft Excel, Golden Software Surfer 12 and the analytical hierarchy process method (AHP) for rating and weighting the contributing eight parameters. The main outcome of this research is the vulnerability classification for each region supported by the corresponding vulnerability map. The study indicated that the highest weight is assigned to the depth to groundwater and soil media parameters while the lowest weight was assigned to the topography factor. The results indicated that, for Al-Minia study area, about 85% of the aquifer is classified as medium vulnerability and about 11% is low to medium and 4% is medium to high. For Wadi Al-Natrun study area, about 67% of the aquifer is classified as medium vulnerability and about 3.3% is low to medium and 28.7% is medium to high. For El Kharga Oasis study area, about 48.8% of the aquifer is classified as medium vulnerability and about 51.5% is low to medium.