Page - 954 - in Book of Full Papers - Symposium Hydro Engineering

routine discharge facilities so as to increase the operating frequency of emptying facilities. Thereby examine their status and repair them if necessary to ensure dams stabilities. EMERGENCY EMPTYING STANDARD AND MANAGEMENT (1) Emergency emptying standard Different from overhauling emptying, extreme disaster at any time of the year must be considered in emergency emptying. Longtan dam for example, two bottom emptying outlets with the size of 5m by 10m were designed to discharge flow of 3210m3/s, 20-year return flood in dry season. However, if it is need to emptying 5-year return flood of the whole year emergently, the flow up to 14400m3/s, 4 more bottom emptying outlets with the same size should be designed, which will increase the investment in great deal. So, it is not economical and reasonable to solve the emergency risk only depending on emptying facilities. It should be deeply researched to choose a proper standard of emergency emptying. (2) Dam emergency management In case of extreme disaster or other risk, the reservoirs water level must be lower down rapidly, which may cause man-made extraordinary flood and bank slops stability problems. For example, the maximum discharge flow of Xiluodu arch dam reaches 49000m3/s, which will wreak destruction to downstream banks. Obviously, a professional emergency management institute at the national level should be set to decide whether to empty and discharge to which water level. So, it is necessary to develop risk assessment mechanism and risk management technology, manage dam safety in case of emergency at the basin cascade and national level, and improve the dam safety management level [3]. SUMMARY Based on summarizing of present design status of reservoir emptying, the key technology problems of lower discharge facilities are analyzed in this paper, and then some subjects need to be further researched are discussed. (1) Reservoir emptying is to discharge the reservoir to a proper water level in order to keep the dam stability instead of discharging the entire reservoir. (2) It is very important and effective to set emptying facilities to lower down the water level in emergency. Characteristics of reservoir and projects as well as hydrologic conditions should all be considered when emptying design to help choosing a reasonable emptying scale and depth. (3) The key technologies of lower discharge facilities should be further researched in the future to break though the limited factors. (4) The basin cascade dispatching and forewarning, manage systems of dams safety adapting to construction and economic level, as well as dams lifecycle safety management and risk distinction system suited to national conditions, should all be established and improved in order to minimize risk of basin cascading dams failure. 954