Su spent five years in Hangzhou as governor of two terms that were eighteen years apart. He wrote a lot about the Cold Spring Pavilion (below left) where he did his work and not at his government office.
West Lake supplied fresh water to the city residents but fast growing water plants often covered the lake in Su’s time. In Su’s first term, he dug four wells as reservoirs in addition to the existing two. He delivered fresh water to the entire city with bamboo pipes from the six wells. He cleared West Lake, almost one third of which was covered by water plants.
Eighteen years later, again the lake was half covered with water plants and the bamboo pipes were broken. The Canals were known for shallow water level and accumulated silt that affected its traffic. Chien Tang or Money Pond River is known for its swirling waves with mud and sand even today (above right). He repaired the six wells, replaced the bamboo with clay pipes connecting them to West Lake and deepened the canals with underground trenches. He used Money Pond Bay as water source of North Canal and West Lake for Salt Canal. He built a fresh water and muddy water lock where the two canals merged in the north. The muddy water lock was shut on high tide to prevent silt and water level of the canal maintained with the other lock to ensure free flow of traffic. He employed welfare to work residents to dredge West Lake, and used dredged piles to build a direct dyke running from north to south, it shortened the long walk meandering along the lakeshore.
Nine pavilions and six bridges were built; willows, magnolia, peach blossoms and hibiscus planted, creating a picturesque promenade when in bloom.