The department shall determine whether an adverse resource impact has occurred under this part and whether a withdrawal is a zone A, a zone B, a zone C, or a zone D withdrawal under this part based upon cumulative withdrawals affecting the same stream reach. In accounting for these cumulative withdrawals, the department shall apply both of the following:

  (a) Beginning on October 1, 2008, the department shall begin water withdrawal accounting for cumulative withdrawals affecting the same stream reach.

  (b) Beginning on February 1, 2009, the department shall adjust the water withdrawal accounting under subdivision (a) such that if cumulative withdrawals beginning on October 1, 2008 have removed a sufficient flow of water from a stream reach to change the zone classification of that stream reach, the department shall reset the water withdrawal accounting benchmark for that stream reach as follows:

  (i) If the cumulative impact of withdrawals on February 1, 2009 results in a classification as a zone B withdrawal, the accounting benchmark shall be reset at the beginning point for zone B withdrawals.

  (ii) If the cumulative impact of withdrawals on February 1, 2009 results in a classification as a zone C withdrawal, the accounting benchmark shall be reset at the beginning point for zone C withdrawals.

  (iii) If the cumulative impact of withdrawals on February 1, 2009 results in a classification as a zone D withdrawal, the accounting benchmark shall be reset at the beginning point for zone C withdrawals. If there is not a zone C for the classification of the stream reach, the water withdrawal accounting benchmark shall be reset at the beginning point for zone B withdrawals.