“Annual overdraft” means the amount, as determined by the board of directors of the replenishment district, by which the quantity of ground water removed by any natural or artificial means from the ground water supplies within such replenishment district during the water year exceeds the quantity of nonsaline water replaced therein by the replenishment of such ground water supplies in such water year by any natural or artificial means other than replenishment under the provisions of Part 6 of this act or by any other governmental agency or entity.