Miss. Code Ann. § 51-29-121: Miss. Code Ann. § 51-29-121

Whenever such districts include within their boundaries land already included in an existing drainage district, such land in the existing district shall remain liable for benefits already assessed or that may thereafter be assessed by such existing district, and shall also be liable to be assessed for benefits by the new district as now provided by law; but such land in an existing district may, for any of its improvements used by the new district, be given credit against the assessment of benefits levied by the new district to the amount of its pro rata portion of all the bonded and outstanding indebtedness, including interest to accrue upon such bonds and indebtedness of such existing district.