The Exploration and Development of Water Resources in Harrat Khaybar
Essam O. Al Wagdani, Ahmed S. Basamed, Hassan H. Al-Shorbaji, Mahmood Thabit, Waheeb A. Al Ashi, and Hassan A. Al Hery
The Khaybar volcanic area is composed mainly of lava flows and underlain by alluvial deposits of various types of sediments (gravel, sand, clay), which rest on Precambrian crystalline rocks—a configuration that provides groundwater potential in the region. Significant water-bearing formations occur in two different lithological units, namely, the sub-basaltic alluvial deposits as well as the basalt flows. Electrical resistivity and electromagnetic surveys suggest the presence of freshwater in good quantity.
On the basis of hydrogeological studies of 633 wells, the average depth to water table is 47 meters and the depth range is 6 to 280 meters. Pumping tests indicate aquifer potential ranging from medium to high based on Ghearghe classification of transmissivity values while storativity values indicate unconfined to semi-confined conditions. The annual recharge rates based on chloride mass balance are rather low with an average not exceeding 0.45 mm attributable to low rainfall of 50 mm/year. Geochemical analyses of 301 water samples indicate cation compositional variation from dominantly Na+ to dominantly Ca2+ and Na+ with relatively lesser amount of Mg2+ and K+. The dominant anions are Cl– and SO42–. In some wells, NO3– and U contents exceed Saudi
Arabian standards. The range of residual sodium carbonate values indicates suitable use for irrigation while values for total salt concentration hazard, sodium adsorption ratio, magnesium hazard, and boron hazard indicate that only a few exceed the limits for safe use as irrigation water.
Al Wagdani, E.O., Basamed, A.S., Al-Shorbaji, H.H., Thabit M., Al Ashi, W.A., and Al Hery, H.A., 2016, The exploration and development of water resources in Harrat Khaybar: Saudi Geological Survey Technical Report SGS-TR-2012-10, 73 p., 67 figs., 19 tables, 1 app.