Wash. Rev. Code § 35.43.045
Every city or town shall have the right of entry upon all irrigation, drainage, or flood control canal or ditch rights-of-way within its limits for all purposes necessary to safeguard the public from the hazards of such open canals or ditches, and the right to cause to be constructed, installed, and maintained upon or adjacent to such rights-of-way safeguards as provided in RCW 35.43.040: PROVIDED, That such safeguards must not unreasonably interfere with maintenance of the canal or ditch or with the operation thereof. The city or town, at its option, notwithstanding any laws to the contrary, may require the irrigation, drainage, flood control, or other district, agency, person, corporation, or association maintaining the canal or ditch to supervise the installation and construction of such safeguards, or to maintain the same. If such option is exercised reimbursement must be made by the city or town for all actual costs thereof.
RCW 35.43.045
Safeguarding open canals or ditches, assessments: RCW 35.43.040, 35.43.045, 36.88.015, 36.88.350, 36.88.380 through 36.88.400, 87.03.480, 87.03.526.