Hydrology for the water management of large river basins : proceedings of an international symposium held during the XXth General Assembly of the International Union of Geodesy and Geophysics at Vienna, 11-24 August 1991 / organized jointly by IAHS, UNESCO and WMO ; ed. by F.H.M. van de Ven, D. Gutknecht, D.P. Loucks, K.A. Salewicz / Wallingford (Oxfordshire - GB) : IAHS Press , 1991