Feasibility of reducing the capacity of plain reservoirs through the joint optimal scheduling of mountain and plain reservoirs

Abstract

Plain reservoirs are critical to water allocation in arid regions due to their low cost and proximity to irrigation areas. However, its remarkable evaporation and seepage losses exacerbate the water resources shortage in arid regions. Therefore, mountain reservoirs present a superior alternative to plain reservoirs owing to their low water loss. This study proposes a joint operational model of mountain and plain reservoirs in arid inland river basin to quantify the potential capacity reduction of plain reservoirs. The Aksu River Basin in China is selected as a case study to evaluate the feasibility of replacing plain reservoir capacity with mountain reservoirs. The results show that mountain reservoirs increased the guaranteed irrigation water supply rate by 18.3 % in the planning year, while reducing the utilization of plain reservoirs. Additionally, the mountain reservoirs tend to store water with priority during high-flow periods, thereby reducing the water storage volume in plain reservoirs. By contrast, plain reservoirs supply water preferentially during periods of deficit. Worthy of note is that, mountain reservoirs still have considerable available storage. In this context, plain reservoirs can be reduced by 1.74 × 10⁸ m³ (74.04 %) in the planning year, saving 0.32 × 10⁸ m³ of water. By comparison, the plain reservoirs should remain unchanged in the current year. In summary, reducing the storage capacity of plain reservoirs in arid basin is conducive to lowering evaporation and seepage losses. This study provides a high-efficient way of utilizing water resources utilizing in arid regions from the viewpoint of reservoir capacity replacement in mountain-plain reservoir systems.