Abdel Ghaffar, M.K.; Soliman M.M. and Azzam, M.A.(( 2013). Hydrological characteristics of drainage basins and groundwater quality in Dakhla Oasis, Western Desert, Egypt.Minufiya J. Agric. Res.Vol.38 No. 6(3): 1713-1728.
Abstract: The current investigation aims are study the hydrological characteristics of drainage basins and ground water quality for drinking and irrigation uses in Dakhla Oasis, Western Desert, Egypt. The hydrological characteristics of the study area are obtained by the application of geographic information system. The study basins, in general, have very small runoff possibilities and the exploitation of the local surface water depends on the local hydrographic and geomorphologic conditions. Flow direction, flow accumulation, catchment areas and drainage lines maps are hydrological characteristics resulted from Arc hydro model application on digital elevation model (DEM) of the study area.
The Nubian Sandstone Aquifer (NAS) is considered the only major fresh water resource in the eastern Sahara including the Dakhla Oasis. There are shallow and deep wells extracting the upper and lower aquifers, respectively, in the Dakhla Oasis. Groundwater is present virtually everywhere in the study area, but conditions for groundwater exploitation varies widely from one zone to another.
For the determination of water quality at the study area, forty four groundwater samples were collected from different wells and chemically analyzed. pH values, electrical conductivity (EC), total dissolved salts (TDS) were determined. Sodium adsorption ration (SAR) values were calculated. Dissolved inorganic constituents, i.e. major cations (Ca++, Mg++, Na+ and K+) and major anions (Cl-, SO4= and HCO-3) and also some trace elements (iron, manganese and boron) were determined.
The TDS and major ions content of the sampled wells are below the critical limits for drinking, however, the trace element contents (Fe and Mn) limit the water suitability for such use. According to the salinity and SAR, most of the sampled water wells are high and moderate suitability classes for irrigation uses with minor of marginally suitable class due to relative shallow wells which exposed to increased groundwater abstraction. The studied water samples properties are mostly under the critical levels of irrigation use except for iron and manganese elements. The studied trace elements showed that about 50% of the studied samples have iron and manganese values above the critical limits of irrigated agriculture. Their pollutant hazard may be depleting under aerobic condition and discharge. The quality of the water does not present special problems when used in irrigation for a short-term.
Keywords: (Dakhla Oasis, Hydrological characteristics, Drainage basins Groundwater )
