The director shall assure, in a manner consistent with existing statutes or rules, that for each category of water body, as described in section 39-3609(1) through (3), Idaho Code, the following limitations shall apply:
(1)  For waters in the "high," category a total maximum daily load or equivalent process as described in this chapter shall be undertaken. Provided however, that nothing in this section shall be interpreted as requiring best management practices for agricultural operations which are not adopted on a voluntary basis.
(2)  For waters in the "medium" category, such changes in permitted discharges from point sources on the water body or to the best management practices for nonpoint sources within the watershed deemed necessary to prohibit further impairment of the designated or existing beneficial uses.
(3)  For waters in the "low" category, such changes in permitted discharges from point sources on the water body or to the best management practices for nonpoint sources within the watershed deemed necessary to prohibit further impairment of the designated or existing beneficial uses.