That the board of county commissioners of any county in this state shall have power, whenever in their opinion the same is demanded by or will be conducive to the public health, convenience, or welfare, to cause to be established, located and constructed, as hereinafter provided, any ditch, drain or watercourse within such county: Provided, That it shall be unlawful to divert any natural watercourse from a well defined channel.
K.S.A. 24-301