4.6　Selection of Dimensions of Power Waterway and Volume of Daily Regulation Pool

4.6.1　For diversion type hydropower stations，the dimensions of headrace and the volume of daily regulation pool shall be selected based on analysis and comparison of landform，geology，ice，sedimentation，installed capacity of the hydropower station and daily operation mode，etc.

4.6.2　The dimensions of headrace shall be selected through comparison of various schemes by calculating the benefit and costs of energy output in each scheme.

4.6.3　The volume of daily regulation pool may be selected according to the storage capacity required for daily load operation after being regulated under the design reliability.The safety factor may be 1.1-1.2.

4.6.4　If there are no restrictions by other authorities in charge of comprehensive utilizations，the volume of daily regulation pools of cascade hydropower stations should be determined by simulating the synchronous operation of the cascade hydropower stations.