Abstract
During periods of significant water shortage or when drought is impending, it is customary to implement some kind of water supply reduction measures with a view to prevent the occurrence of severe shortages (vulnerability) in the near future. In the case of operation of a water supply reservoir, this reduction of water supply is affected by hedging schemes or hedging policies. This research work aims to compare the popular hedging policies: (i) linear two-point hedging; (ii) modified two-point hedging; and, (iii) discrete hedging based on time-varying and constant hedging parameters. A parameterization-simulation-optimization (PSO) framework is employed for the selection of the parameters of the compromising hedging policies. The multi-objective evolutionary search-based technique (Non-dominated Sorting based Genetic Algorithm-II) was used to identify the Pareto-optimal front of hedging policies that seek to obtain the trade-off between shortage ratio and vulnerability. The case example used for illustration is the Hemavathy reservoir in Karnataka, India. It is observed that the Pareto-optimal front that was obtained from time-varying hedging policies show significant improvement in reservoir performance when compared to constant hedging policies. The variation in the monthly parameters of the time-variant hedging policies shows a strong correlation with monthly inflows and available water.
Highlights
The rule or policy of any reservoir operation involves deciding the amount of releases to be made from the reservoir to meet the specified demands for different purposes based on the “current storage in the reservoir and the expected inflows to the reservoir”
The study examined the performance of the reservoir simulation model while using time-varying hedging (TVH) policies and compared with the constant hedging (CH) policies
A parameterization-simulation-optimization (PSO) framework is used for obtaining compromising hedging policies for the operation of a reservoir
Summary
The rule or policy of any reservoir operation involves deciding the amount of releases to be made from the reservoir to meet the specified demands for different purposes based on the “current storage in the reservoir and the expected (likely) inflows to the reservoir” (available water). The standard operation policy is a simple operating rule for a reservoir, which aims to meet the demand in each period based on the available water in the current period. If the available water is less than the demand, the available water is released towards meeting the demand. This policy is likely to result in high volumes of deficits in the future periods of operation. In order to avoid severe water deficits during drought periods or when drought is impending, hedging is done, which reduces water supplies proactively and conserves more water for future use [1]
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