1. China Institute of Water Resources and Hydropower Research, and Dept. of Hydropower and Hydraulic Engineering, Tsinghua Univ., Beijng 100038, China.
2. Professor, Dept. of Hydropower and Hydraulic Engineering, Tsinghua Univ., Beijing 100084, China (corresponding author).
3. Chair Professor, Dept. of Civil Engineering, Indian Institute of Technology, Kharagpur, 721302 West Bengal, India.