The study was undertaken to develop methodologies for establishing the legally prescribed minimum flows and levels in streams and lakes in the State of Washington. As more states attempt to preserve their natural resources through the enactment of legislation, their efforts provide a valuable experience record. But, in establishing 'minimum' or 'base' flows in streams for the protection of natural values the development of methodology to apply the laws has not been accomplished and is of particular concern to both state and federal agencies. The overall objective of this study has been to develop methods for analysis of the quantity, quality and economic factors associated with the establishment of low-flow criteria for conservation, recreation and aesthetic purposes. (Modified author abstract)