When lands in an existing district, and which have been assessed for benefits, are acquired for rights of way by such districts for canals, ditches, levees, floodways, by-passes, or other necessary drainage purposes, assessments already levied or that may be levied against such land to pay its proportion of outstanding bonds or other obligations of the existing district, including all interest to accrue thereon, shall be assumed and paid by the new district so taking or so acquiring such land, in the proportion that its value, as fixed by condemnation, shall bear to the value of the land included in the entire district.