A leading water-resource geographer outlines a series of measures that, in his view, would assure mankind with an unpolluted water supply for many more generations. He opposes the view that inland waters are virtually lost to man as a source of water and that other sources such as desalting of seawater or melting of icebergs must be sought. The proposed measures envisage the gradual reduction and ultimately halting of the discharge of wastes and sewage into streams and lakes by the use of municipal sewage for irrigation of forage crops near urban centers and the provision of closed water systems within industrial plants, including treatment and reuse of wastes.