Abstract: Calculation method for roughness coefficient of water conveyance tunnel in Jinping Ⅱ hydropower station is summarized in this paper. Two viewpoints are presented: (1) in order to improve the calculation accuracy, we should select the section of tunnel where local loss is smaller to calculate roughness coefficient and the bottom velocity head should be included; (2) during the calculation of average hydraulic radius of the diversion tunnel, the method of equal volume or equal momentum cannot be used. The principle of equal equivalent water loss should be followed.

Key words: roughness coefficient, section area, hydraulic radius

摘要： 就锦屏二级电站引水隧洞，根据实测水头损失、反算沿程水头损失糙率系数过程中的一些经验和认识进行总结，提出了：（1）应尽量选取局部损失所占比例较小的洞段来计算沿程水损，并应计入测点底部流速头，以提高计算精度；（2）在引水隧洞平均水力半径的计算过程中，不能采用等动量或者等体积的方法，必须遵循水损相等的原则进行当量等观点，供参考。

关键词: 沿程糙率系数, 断面面积, 水力半径