Nothing in title 25 of this article shall be held to curtail the
powers of the department as to river or drainage work within a river
regulating district prior to the time that such district is charged with
the powers and duties above set forth as to river or drainage work or
both, nor in any event shall the powers of the department under sections
15-1945 and 15-1957 be curtailed or changed. Should the department at
any time form or have formed a river or drainage improvement district in
a basin now or subsequently formed into a river regulating district,
which district is later given the extended powers herein provided, such
river or drainage improvement district shall become a sub-district
administered by the board. In such cases, all outstanding indebtedness
and financial liabilities of the district shall remain undisturbed and
not in anywise altered by the transfer and shall be met by the board.