一项水利工程完工投产以后,其各年的技术、经济和对环境影响的状况是不尽相同的。对一项工程或几个工程比较方案进行经济分析评价时,不能只观察研究其在某一年或某一段时期内的各种表现,而应根据工程的寿命长短 After a water conservancy project is completed and put into production, its technical, economic, and environmental impacts are not the same in each year. When conducting economic analysis and evaluation of a project or several project comparison programs, it is not possible to observe only the various performances of a project during a certain year or a certain period of time. Instead, it should be based on the length of life of the project.