For a city with 733km of coastline, an internationally famous harbor and 262 islands, water quality is extremely important and is a key facet of public health policy. Hydro-environmental engineering research is vital to the understanding of issues such as protection of our beaches, red tides, fisheries management and even the recently reinstated cross-harbor swimming race. Professor Lee specializes in environmental hydraulics & fluid mechanics and water-quality modeling. In this talk, he discusses the relationship between sustainable water management and “turbulent vortices” within the sea, and the development of a real-time, beach water-quality forecast system that every smart city should have. He also reports on recent research related to chlorine disinfection dosages for the second stage of the Hong Kong Harbour Area Treatment Scheme – the largest project of its kind in the world. The use of real-time forecast systems for the Kowloon East Smart City will also be discussed, along with other international examples.