Finds that participants in the Walla Walla watershed pilot program have demonstrated exceptional cooperation in developing and implementing an innovative water management concept that enhances flexibility in water use since convening in 2009.

Requires the existing authorities and structure of the pilot program to evolve to: (1) Meet the growing water resource demands in the watershed; and

(2) Protect and enhance ecological functions.

Extends the pilot program through June 30, 2021, to: (1) Allow it to perform internal and external evaluations;

(2) Build upon previous pilot program efforts;

(3) Continue Walla Walla river flow enhancement technical work; and

(4) Develop a thirty-year integrated water resource management strategic plan.

Imposes additional duties on the water management board during the transition period of July 1, 2019, to June 30, 2021.