The counties and municipalities located within the boundaries of the irrigation district or districts to be established by the provisions of this article are hereby authorized and empowered to contribute to the work of the agency any amount or amounts of money that their respective governing bodies, acting in their sole discretion, shall approve to be paid from the general fund of the respective counties or municipalities. Governing bodies of such counties or municipalities are hereby empowered to levy and collect ad valorem taxes within constitutional limits for such purposes, which are hereby declared to be for municipal and county public purposes.