Bicriterion operation of a water resources system with reliability-based tradeoffs

摘要

The weekly operation of a water resources system under the two conflicting objectives of irrigation and water quality demand is analyzed. The real life case of the Neste river system in Southwestern France consists of mountains, reservoirs, and conveyance facilities designed to irrigate up to 30,000 hectares and to augment low flows of the rivers to maintain their quality. A stochastic dynamic programming model under reliability constraints has been constructed in which the trade-off point between criteria is controlled by two parameters: β, which trades off water quality with the expected lengths of the irrigation period, and α, which trades off water quality in the two main rivers of the system (Neste and Gascogne). Using stochastic simulation, trade-off curves are obtained between the average final storage volume and storage failure index (vulnerability), and between the crisis frequency and water quality index. The procedure thus allows the system manager to formulate and quantify objectives in a rational way; furthermore, the consequences of decision in a “crisis” situation, when all farmers have to suspend irrigation, can be evaluated.