Drainage districts heretofore organized under the provisions of any law and amendments thereto not brought forward in this code shall have the privilege of continuing to operate under such law, and the adoption of this code shall not be held to repeal any such law or laws and amendments thereto, in so far as such districts are concerned. However, all drainage districts hereafter created must be organized and shall operate under the provisions of Chapters 29, 31 and 33 of Title 51, Mississippi Code of 1972.