Canadian Asit Biswas (3rd R), winner of the Stockholm Water Prize in 2006 and guest professor at the National University of Singapore, and his Mexican wife Cecilia Tortajada  (4th R), professor with the university’s Institute of Water Policy — Lee Kuan Yew School of Public Policy, visit the Dashahe U-Station in Nanshan District that safeguards the water environment in the region yesterday. They were in Shenzhen to attend a voluntary river chief forum.   (Story on P3)Sun Yuchen