Planning reservoir operations with imprecise objectives

Imprecise and noncommensurable objectives for reservoir operation are addressed through fuzzy dynamic programming using an implicit stochastic approach. Fuzzy membership functions for evaluating the achievement of a linguistically described operational goal and linguistically described constraints are estimated from surveys of decision makers. Summary statistics of the membership function values for optimal operation provide easily interpreted measures of degree of satisfaction among diverse objectives. An example application to the proposed Grey Mountain Reservoir on the Cache la Poudre River in northern Colorado showed that the expected degree of satisfaction for water supply objectives (constraints) would exceed 70% in six of 12 months, while 90% satisfaction of the flood control objective could be expected throughout the year. Expected degrees of satisfaction for storage, recreational, fish habitat, and hydropower objectives are substantially lower. Relative variability in predicted degrees of satisfaction is high. The average composite degree of satisfaction for the project is moderate, has a general seasonal trend, and is substantially variable in late summer and early fall.