RCW 89.30.436

In any instance where the construction, reconstruction, betterment or extension of power and/or irrigation works or the acquisition of property and rights therein appropriate for the purpose of carrying out the provisions of this chapter, will specially benefit any or all the lands within the reclamation district susceptible of irrigation, the district board shall have authority to organize said lands into a general improvement district and to provide for the levy and collection of special assessments against said lands to raise revenue in support of any or all of said purposes.