Phayao Lake is the 3rd biggest lake in Thailand followed by Bueng Borapetch (Nakornsawan) and Nong Harn (Sakolnakorn), respectively. Even though Kwan Phayao is 3rd largest lake in Thailand, but Kwan Phayao is the largest source of fresh water in upper north with 12,831 rai.

In past dry season lead Kwan Phayao has 2 basins; Kwan Luang and Kwan Noi. In contrast, a flood covered the overall area in flood season, and then Fisheries Department constructed a dam to obstruct Ing River in 1941, this makes Kwan Phayao has stable level of water with average 1.5 meters depth and also acts as largest inland fishery station in the north. Kwan Phayao also discovers the breeding of giant-catfish in 1983 which is the first discoverer of the world.