This code is revised from DL/T 5084—1998 Technical Code of Hydrology for Electrical Power Projects by East China Electric Power Design Institute of China Power Engineering Consulting Group Corporation in collaboration with associated organizations as required by the Notice on Issuance of Plan for Development of Industry Standards in 2006 issued by the General Office of National Development and Reform Commission (FGBGY [2006] No.1093).During the revision, the revision panel conducted extensive investigations, carried out special studies and lab tests, summarized experience in works on hydrometeorology of domestic electrical power projects in recent years, and collected comments from all interests concerned all over China. This code was then finalized through repeated discussions, revisions and improvements, as well as review and revision by experts.