For the purposes of this act the bed and channel of any river in this state or bordering on this state to the middle of the main channel thereof and all islands and sand bars lying therein shall be considered to be the property of the state of Kansas unless this state or the United States has granted or conveyed an adverse legal or equitable interest therein since January 29, 1861 A.D., or unless there still exists a legal adverse interest therein founded upon a valid grant prior thereto: Provided, That nothing in this act shall affect or impair the rights of any riparian landowner or lawful settler upon any island which is state school land.
K.S.A. 70a-106