1. Principal Engineer, Water Resource Center, Tetra Tech, Inc., 10306 Eaton Place, Ste 340, Fairfax, VA 22030 (corresponding author).
2. Assistant Professor, College of Environmental Science and Engineering, Peking Univ., Beijing 100871, China.
3. Associate Professor, Dept. of Civil and Resource Engineering, Dalhousie Univ., Halifax, NS, Canada B3J 1Z1.
4. Professor, College of Environmental Science and Engineering, Peking Univ., Beijing 100871, China.