The managers may initiate an amendment of a watershed management plan or revised watershed management plan by submitting a petition with the proposed amendment to the board. The board must give notice and hold a hearing on the amendment in the same manner as for the watershed management plan. After the hearing, the board may, by order, approve or prescribe changes in the amendment. The amendment becomes part of the watershed management plan after approval by the board. The board must send the order and approved amendment to the entities that receive an approved watershed management plan under section 103D.401, subdivision 5.