Impact of Hydroclimate Change on the Management for the Multipurpose Reservoir: A Case Study in Meishan (China)

Abstract

China holds the largest amount of reservoirs in the world, while more than 80% of them were constructed 50–70 years ago and are approaching a critical stage of their designed lifetime. Before deciding the future of a reservoir, it is essential to find out whether it could still satisfy its original purpose in the context of hydroclimate change under global warming. Here, we present a case study of the Meishan reservoir in east-central China, which was primarily built for irrigation and flood control in the 1950s. We evaluate the impacts of rainfall change on the hedging and releasing rules over the historical period (1969–2008) by instrumental data and future period (2061–2100) based on simulations in a regional rivalry-mitigated scenario from the Coupled Model Intercomparison Project Phase 6. The main conclusions are as follows: (1) the annual total rainfall has a remarkable increasing trend from 2015 to 2100 and the annual precipitation variability exceeds the envelope range during the past 50-year period. The increased precipitation amount mainly occurs in spring (March to May). (2) The optimal regulation cycle is from September to August and from July to June for both historical and future periods. The limiting level during the nonflooded season is lower than the operating water level for more than five months in the historical period, which limits the ability of reservoir regulation and utilization of water resources. However, the water supply is no longer affected by flood control in 2061–2100 because of the redistribution of annual precipitation. (3) The projected irrigation and residential water demands of the Meishan reservoir are stable; thus, the improvement of the total economic benefit will mainly depend on power generation. This case provides a practical guide for many reservoirs serving water supply for small cities in eastern China, where the size of the population and cultivated land area is stagnant and the climate is getting wetter.