The storage problem for infinite reservoirs where annual inflows are distributed as independent gamma variables is treated in this paper. After having determined the distribution of the water content in the reservoir under consideration for a given period, an attempt was made to derive the expressions for the first four moments of the surplus and deficit, and then to approximate their distributions by the Type I curve using the Pearson criterion. The expected value of the range was also derived, and its variance was approximated by a linear equation of the reservoir life. Finally, the distribution of the range was approximated by the Type III curve.