The cost of constructing, acquiring, purchasing, or maintaining the canals, ditches, reservoirs, reservoir sites, water, water right, rights-of-way, or other property incurred in connection with any irrigation project under said irrigation district laws shall be equitably apportioned among lands held under private ownership, lands legally covered by unpatented entries, and unentered public lands included in said irrigation district. Officially certified lists of the amounts of charges assessed against the smallest legal subdivision of said lands shall be furnished to the officer designated by the Secretary of the Interior of the land district within which the lands affected are located as soon as such charges are assessed; but nothing in this chapter shall be construed as creating any obligation against the United States to pay any of said charges, assessments, or debts incurred.

All charges legally assessed shall be a lien upon unentered lands and upon lands covered by unpatented entries included in said irrigation district.