In deciding monthly volumetric limits for a water allocation to take unsupplemented water, the chief executive must have regard to—
(a) the local availability of water in each month; and
(b) the conditions under which the water may be taken under the authorisation; and
(c) the volumes of water estimated by the chief executive to have been taken under the authorisation during the period, of not more than 10 years, immediately before the commencement of this plan; and
(d) the simulated mean annual diversion; and
(e) the efficiency of the use of the water mentioned in paragraph (c).