1. Professor of Water Resources, Civil and Environmental Engineering Dept., Faculty of Engineering, UAE Univ., P.O. Box 17555, Al Ain, United Arab Emirates (corresponding author).
2. Geology Dept., Faculty of Science, Assiut Univ., 71516 Assiut, Egypt.
3. Water Resources Div., Ministry of Environment and Water, P.O. Box 1509, Dubai, United Arab Emirates.
4. Senior Lecturer, School of Engineering, Computer Science and Mathematics, Univ. of Exeter, North Park Rd., Exeter EX4 4QF, U.K.