Wash. Rev. Code § 90.03.255
The department shall, when evaluating an application for a water right, transfer, or change filed pursuant to RCW 90.03.250 or 90.03.380 that includes provision for any water impoundment or other resource management technique, take into consideration the benefits and costs, including environmental effects, of any water impoundment or other resource management technique that is included as a component of the application. The department's consideration shall extend to any increased water supply that results from the impoundment or other resource management technique, including but not limited to any recharge of groundwater that may occur, as a means of making water available or otherwise offsetting the impact of the diversion of surface water proposed in the application for the water right, transfer, or change. Provision for an impoundment or other resource management technique in an application shall be made solely at the discretion of the applicant and shall not otherwise be made by the department as a condition for approving an application that does not include such provision.
This section does not lessen, enlarge, or modify the rights of any riparian owner, or any existing water right acquired by appropriation or otherwise.
RCW 90.03.255
Findings-Purpose-1997 c 360: "The legislature finds that in many basins in the state there is water available on a seasonal basis that is in excess of the needs of either existing water right holders or instream resources. The legislature finds that excess waters often result in significant flooding and damage to public and private resources. Further, it is in the public interest to encourage the impoundment of excess water and other measures that can be used to offset the impact of withdrawals and diversions on existing rights and instream resources. Further, in some areas of the state additional supplies of water are needed to meet the needs of a growing economy and population. The legislature finds there is a range of alternatives that offset the impacts that should be encouraged including the creation, restoration, enhancement, or enlargement of ponds, wetlands, and reservoirs and the artificial recharge of aquifers.
The purpose of this act is to foster the improvement in the water supplies available to meet the needs of the state. It is the goal of this act to strengthen the state's economy while maintaining and improving the overall quality of the state's environment." [ 1997 c 360 s 1.]