(a) In litigation in which the rate of flow of water that would exist in the absence of an impoundment is in issue, that rate shall be deemed to be the minimum average flow for a period of seven consecutive days that have an average recurrence of once in 10 years unless a party to the litigation introduces a calculation that more closely approximates the actual rate. A determination made by the Commission (i) of either that minimum average flow, or (ii) that adopts a calculation that more closely approximates the actual rate of flow, and introduced by one of the parties to the litigation, shall be prima facie correct.
(b) The Commission is authorized to make the determinations specified in subsection (a) of this section and to require the submission of such reports and such inspections as are necessary to permit those determinations.