Spatio-temporal characterization of the Pliocene aquifer conditions in Wadi El-Natrun area,Egypt |
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| Authors: | Alaa A Masoud Mohamed G Atwia |
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| Institution: | (1) Geology Department, Faculty of Science, Tanta University, Tanta, 31527, Egypt |
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| Abstract: | Wadi El-Natrun area has recently undergone extensive urban and agricultural expansion. Due to the absence of natural surface
irrigation supplies, the only source of water in the area is the Pliocene groundwater aquifer. As a result, secondary salinization
from increased abstractions is the major threat to the groundwater aquifer. There is a dire need for efficient strategies
to ensure long-term sustainability of the area’s productive agriculture. These strategies should be based on scientific spatio-temporal
monitoring and analysis of the groundwater conditions that is also lacking. To capture the spatio-temporal variability in
groundwater conditions, field measurements of total dissolved solids, electrical conductivity, pH, temperature, and water
level as well as lab-based ionic composition were performed on 47 groundwater samples collected during 2006 and 2007. Determinations
of the hydrochemical characteristics, water types, salt assemblages, and the sodium adsorption ratio were carried out on the
samples. Reference data sets recorded in 1973 and 1997 were available for the area and were used to monitor the changes occurred
in these periods. Geographic information system (GIS) was appraised for mapping and for integrated analysis of the different
layers. Remotely sensed change detection techniques were applied to the Landsat TM and the ETM + imageries and used to highlight
the extensive reclamation and urbanization and to find key trends for the alterations in the groundwater conditions and their
spatial association with land covers. Results revealed a topographic depression-induced flow pattern, predominance of leaching
and dissolution processes, the presence of saline lakes, over-pumping from the Pliocene aquifer, and temporal changes in land
uses are the main factors combined to control the spatio-temporal variability in the groundwater. Results also clarified the
presence of two: northwestern and southeastern zones that varied distinctively in their hydrodynamic and hydrochemical characteristics.
The northwestern zone showed an average water level decline of 15 m, the water of which is brackish (av. 2,037 mg/l) with dominant Na+, Cl− and SO4
2− ions. The groundwater of this zone is characterized by high to very high salinity hazard and high to very high alkali hazard
and is not recommended for irrigation on soils with poor drainage and without proper management for salinity control. The
southeastern zone showed water level decline less than 2 m, the water of which is fresh (av. 424 mg/l) with major Na+, HCO3
−, Cl−, and SO4
2− ions, and quality suitable for irrigation with medium to high salinity and low to medium alkali hazards. The article represents
the first step towards an integrated management of Wadi El-Natrun groundwater resources within a GIS framework. |
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