The Biyagama Water Treatment Plant or BWTP is a water treatment facility located at the bank of Kelani River, in Biyagama, Sri Lanka.

At a daily output capacity of 160,000,000 L/d (1,900,000 L/ks), it is the second largest water treatment facility in the country.

The plant provides drinking water to approximately one million people, in Wattala, Ja-Ela, Kelaniya, Biyagama, Ragama, Kandana, Kadawatha, Kiribathgoda, Seeduwa and Ganemulla, within the Gampaha District.

[2] The Kelani Right Bank Water Supply Project - Phase 2 is a Rs.

The expansion project is ongoing as of June 2019, by Maga Engineering and Suez.