1. Rural Engineering Research Center, Ministry of Agriculture; B.P. no. 10, Ariana 2080 Tunis Tunisia
2. Dep. of Water Resources Engineering; Univ. of Lund; Box 118 S-221 00 Lund Sweden
3. Dep. of Civil Engineering (SUIKO); Kyushu Univ.; 6-10-1 Hakozaki, Higashi-ku Fukuoka 812 Japan