Subdistricts may be formed by owners of land in main districts theretofore established in the manner provided for the organization of main districts. Such subdistricts shall have the right to use the ditches or canals of the main districts for outlets. The formation of subdistricts shall not operate to release the lands in any subdistrict from the payment of any assessment or levy made prior to the formation of such subdistricts, nor from any assessment which may thereafter be made for the completion and maintenance of the canals in main districts, or for the payment of the principal and interest on any indebtedness incurred by the main district, nor shall it give the subdistrict any claim on the funds of such main district for its local use. It shall be the duty of the drainage commissioners of the main district to control all matters pertaining to the main district drainage. Drainage commissioners for the subdistricts shall have authority and control over all matters pertaining to drainage within their respective subdistricts, except such work as belongs exclusively to the main district. (1917, c. 152, s. 8; C.S., s. 5373.)