GIS-based evaluation and statistical determination of groundwater geochemistry for potential irrigation use in El...

The El Moghra area is located in northwestern Egypt in the Western Desert. It is classified as the first priority of the national project to reclaim 1.50 million feddan of Egypt's desert lands. Groundwater quality assessment of the El Moghra aquifer is essential because irrigation water requirements in the El Moghra area depend solely on groundwater. A geochemistry analysis was conducted for 230,000 feddans from forty-six groundwater samples collected during the drilling process of deep wells in year 2018 and 2019. Our study's main objective is to determine whether the groundwater in the El Moghra aquifer is suitable for irrigation use. ArcGIS was used to prepare the geospatial distribution maps of major elements. Hydrochemical characteristics and groundwater types were identified from descriptive analyses of groundwater samples. Multivariate statistical analysis was run using SPSS; correlation coefficients were first determined; then, a correlation matrix was generated. Principal component analysis was performed and a covariance matrix with varimax rotation was produced. Results revealed the alkalinity and the high salinity of groundwater in the project study area. Most of the samples had a total hardness greater than 300 mg/l. Sodium chloride (Na-Cl) is the dominant type for groundwater samples. The mechanism controlling groundwater chemistry depends on rock weathering. Principal component analysis results showed that two eigenvectors among ten have a 72.86% contribution to the cumulative variance. The higher TDS values (14,008 mg/l) confirm the ions release when the upward groundwater flow from the lower Nubian Sandstone aquifer system to the upper quaternary aquifer occurs. Additionally, the geospatial maps of ion distribution showed that the frequent release of minerals happens in the northwestern part of the project study area: the eastern Qattara Depression. A perfect correlation between sodium and chloride distributions was obtained, and it is identical to the electrical conductivity distribution as well. Our study recommends very salt-tolerant crops as canola, barley, quinoa, and jojoba to be planted in the project area. Drought-tolerant crops as Barbary fig and Jatropha are also recommended. Applying irrigation water frequently with short intervals between irrigations to avoid soil drying and surface clusters' formation, as well as enhance leeching of salts away from the root systems, is essential.