The Oklahoma Water Resources Board shall, from time to time as may be necessary for the economical and satisfactory apportionment of the water, divide the state in conformity with the drainage areas, into water districts to be designated by name and to comprise, as far as possible, one or more distinct stream systems in each district. The districts may be changed from time to time as may in its opinion be necessary for the economical and satisfactory apportionment of the water.
Okla. Stat. tit. 82, § 1085.3