2.1 Overview of the study area
This study selected Shahe Reservoir (118°07′ − 118°15′E, 32°20′ − 32°26′N), Huanglishu Reservoir (118°01′ − 118°07′E, 32°11′ − 32°16′N), and Chengxi Reservoir (118°15′ − 118°18′E, 32°19′ − 32°22′N) as the research objects in Chuzhou City (Fig. 1). Shahe Reservoir is located in Shahe Town, Nanqiao District, Chuzhou City, was built in September 1958, has been reinforced and expanded for five times, reached the current scale in 1979. The reservoir has a catchment area of 300 km2 and a total capacity of 197 million m3, as a large (Ⅱ) type reservoir, it is mainly used for irrigation and has the comprehensive benefits of flood control, urban water supply, aquaculture, and so on. Huanglishu Reservoir is situated in Chuzhou City, Quanjiao County, started construction in September 1959, and in December 1965 was completed. With a control basin area of 262 km2 and a total reservoir capacity of 315 million m3, it is a large (Ⅱ) type reservoir that is mainly used for irrigation, taking into account the comprehensive roles of flood control, water supply, power generation, and aquaculture. Now renamed Biyun Lake, the surrounding area has become very popular for tourism. Chengxi Reservoir lies in the upper reaches of the tributaries of the Qingliu River in Chuzhou City, constructed in 1958 and put into operation in 1965. Reinforcement was carried out in 2010 and is now completed. The control basin area of the reservoir is 168 km2 and the corresponding capacity is 85.25 million m3, which has the functions of flood control and security, urban water supply, agricultural irrigation, power generation, and so on. The average annual water supply is about 29 million m3 to the city and 9 million m3 to agriculture. It can be clear that guaranteeing the domestic water needs of Chuzhou residents is the major task of the Chengxi Reservoir.