For the purposes of this chapter the following definitions shall apply:

(1) "Department" means the Washington state department of ecology.

(2) "Groundwater right" means an authorization to use groundwater established pursuant to chapter 90.44 RCW, state common or statutory law existing prior to the enactment of chapter 90.44 RCW, or federal law.

(3) "Withdrawal facilities" means and includes any well, infiltration trench or other excavation that is drilled, cored, bored, washed, driven, dug, jetted or otherwise constructed, together with the casing, screen, pump, pump column, motor and related equipment which is used for the withdrawal of groundwater.

(4) "Aquifer" means any geologic formation that will yield water to a well or other withdrawal facilities in sufficient quantity for beneficial use.

(5) "Groundwater" means all waters that exist beneath the land surface or beneath the bed of any stream, lake or reservoir, or other body of surface water, whatever may be the geological formation or structure in which such water stands or flows, percolates or otherwise moves.

(6) "Multiple aquifer system" means any geologic formation(s) which contains distinct aquifers at different depths that exhibit a significant degree of local or regional hydraulic separation.

(7) "Upper aquifer zone" means all aquifers within a multiple aquifer system lying between the land surface and a depth or geologic formation, as determined by the department consistent with the purposes of this chapter, or as set forth in the groundwater subarea management program for the area, if one exists.

(8) "Lower aquifer zone" means any aquifers occurring at a depth below the upper aquifer zone, as determined by the department, or as set forth in the groundwater subarea management program for the area, if one exists.

(9) "Cascading waters" means any groundwaters which fall or flow through a well or other withdrawal facilities, from one groundwater aquifer to another.

(10) "Rehabilitation of withdrawal facilities" means the work necessary to reconstruct or modify existing withdrawal facilities in order to bring them into conformance with applicable laws, regulations, permit or certificate provisions and orders of the department.