(1) This chapter applies to public surface waters of the main stem of the Snake River in Washington and to any groundwater where the groundwater is determined by the department of ecology to be part of or tributary to the surface waters of the main stem of the Snake River. For purposes of this chapter, the main stem of the Snake River extends from the Idaho, Oregon and Washington border, in the extreme southeastern corner of the state of Washington, at river mile 175, to the confluence with the Columbia River near Pasco, Washington at river mile 0.

(2) Nothing in this chapter shall affect existing water rights, riparian, appropriative, or otherwise, existing on the effective date of this chapter, including existing water right permits and certificates.