257.020.  Definitions. — Unless the context requires otherwise, as used in this chapter the following terms mean:

  (1)  "Court", the circuit court wherein the petition for the organization of the district was filed and granted;

  (2)  "Person", person, firm, copartnership, association or corporation;

  (3)  "Public corporation", counties, townships, cities, towns, villages, all special districts, and all other governmental agencies;

  (4)  "River":

  (a)  The main stream and its tributaries of a primary drainage basin;

  (b)  The main stream and its tributaries of a secondary drainage basin;

  (c)  The principal stream of a tributary drainage area and its tributaries;

  (d)  The stream or streams of an unnamed drainage area, the specific delineation of which is otherwise provided for herein;

  (5)  "River basin":

  (a)  A primary drainage basin; and including all of the area of a primary drainage basin above the point where the main stream of such basin flows out of the state of Missouri;

  (b)  A secondary drainage basin;

  (c)  A tributary drainage area, the principal stream of which drains directly into the main stream of a primary or secondary drainage basin; or

  (d)  The unnamed drainage areas not within any primary drainage basin and including those areas which border and drain directly into the Mississippi, Missouri, or Des Moines Rivers; all such basins and areas, and the streams thereof, being those delineated on the Missouri Bureau of Geology and Mines Drainage Map of 1927 as prepared and drawn under authorization of Laws of Missouri, 1921, page 88, and which drainage map was accordingly made of record in the bureau's biennial report of the state geologist transmitted to the 54th general assembly in 1927.  Such delineation of basins and areas shall be understood to define their general locations and names, if any, and to be not definitive of their exact boundaries.