Department of Geology, University of Kuwait, P.O. Box 5969, Safat 13060, Kuwait
ABSTRACT
The primary objective of this study was to determine to what extent the direct current resistivity method can be applied to locate the brackish/saline water interface and delineate the extension of shallow water-bearing formations in the Kuwait Group. The method was tested in the Al-Abdali area, located in the extreme north of Kuwait and occupying an area of
76 km2. In addition, studies of groundwater chemistry were carried out to identify water type, range of salinity and suitability of the groundwater for irrigation. Accordingly, thirty-four vertical electrical soundings (V.E.S.) were made, using the Schlumberger configuration AB/2 up to 316 m and 1-2 km apart. The manual and arithmetic interpretations of 34 V.E.S. measurements reveal that there are four major layers. The first two layers down from the surface have a wide range of resistivity values of 10-3500 ohm-m, and refer to dry sand and sand with gravel through to moist sand and gravel. The third layer shows a large drop of resistivity to 5-45 ohm-m which may be an indication of a brackish water saturated zone. The fourth layer has a very low resistivity of < 1-3 ohm-m and represents saline groundwater. The contour map of measured apparent resistivity values (pa AB/2 = 147 m showed a gradual decrease of resistivity in a S-W to N-E direction. For the purpose of studying groundwater chemistry, 36 samples were collected and analysed for major ions, E.C., pH and trace elements. It was found that the water is mainly a brackish, NaCl water type. The total dissolved solids range from 4,000 to 8,000 mg/l, increasing in the northeasterly direction. The suitability of the groundwater for irrigation has been judged from its E.C., sodium adsorption ratio, and boron content as well as from some trace elements. The calculated values of sodium adsorption ratio (S.A.R.) range from 9-2 to 20.5 and this corresponds to a high sodium water, which is generally unsatisfactory for irrigation purposes in fine-textured soil. Moreover, the E.C. ranges from 5,500 to 13,000 pmhos/cm which isconsidered extremely high salinity water, that is recommended only for permeable, welldrained soils.