Water Release Policy Effects on the Shortage Characteristics for the Shihmen Reservoir System during Droughts

Drought-induced shortages are inevitable because of unexpected abnormal dry weather and the increasing need for water resources. Therefore, assessment of possible shortage conditions for a specific water supply system is an essential component in water resources planning and management. In this study, the shortage characteristics for the Shihmen Reservoir in Taiwan are investigated. A description of the reservoir yield in terms of the shortage frequency, magnitude, and duration is developed first. The derived reservoir yield description under a given operating policy and demand includes the reliability, total shortage rate, frequency, single period shortage, event shortage duration and magnitude, and interarrival time of shortage events. Hedging is a common measure adopted in reservoir operation that involves accepting a small current deficit to reduce future severe shortages. The reservoir supply index is then developed to trigger hedging in this study. The shortage characteristics for different lead-time hedging rules show that the derived reservoir supply index is a useful indicator for triggering hedging and the differences among reservoir performance for various release policies are easily compared using the derived reservoir yield description in terms of probabilistic shortage characteristics. Copyright Kluwer Academic Publishers 2003