Yen Bai province has 03 main river systems of the Red River, Chay River and Nam Kim stream with total length of 320 km, catchment area is over 3.400 km2. Tributary system is rather evenly distributed across the province. Due to the characteristics, the rivers and streams are derived from high mountain with a steep slope so these are abundant potentials for hydropower and water supplying for production and daily life of local people.
The Red River flows through the area of Yen Bai with 100 km long, with 48 tributary streams (including 4 large streams: Ngoi Thia, Ngoi Hut, Ngoi Lau and Ngoi Lao), the catchment area is 2,700 km2. The Chay river flows through the area of Yen Bai with total length of 95 km, with 48 tributary streams, the catchment area is 2.200 km2
System of ponds and lakes with the area of 23.400 ha, of which Thac Ba lake has an area of 19.050 ha. This is a favorable condition for development of aquaculture and eco-tourism development. With the steep slope, Thac Ba Hydropower Plant, the first hydropower plant in Viet Nam, was built in the downstream. Nam Kim stream has total catchment area of 600 km2 and this is a branch of the Da river, with steep slope, it will be able to develop the hydropower.
System of ponds and lakes with the area of 20.913 ha, of which Thac Ba lake has an area of over 19.050 ha. This is the potential for development of aquaculture and tourism.