The Pooled Money Investment Board shall, at such times as it deems necessary, determine whether any portion of the money theretofore transferred to and remaining in the Surplus Money Investment Fund from any special fund is needed by such special fund to carry out the purposes for which it was created; and if so, it shall determine the amount thereof. Thereupon, it shall reduce the amount of surplus money theretofore designated with respect to such special fund by the amount determined to be needed by such fund. Upon such reduction of the surplus money in any special fund, the State Treasurer shall, on order of the State Controller, transfer from the Surplus Money Investment Fund to such special fund an amount of money equal to that by which the surplus money of such fund was reduced.