Report documenting the development of the HEC-Prescriptive Reservoir Model and its application of analyzing the operation of the Columbia River reservoir system. The model represents the system as a network and uses network- flow programming to allocate optimally the system water. Two applications are documented: (1) a validation test to determine the applicability of the model for the system, and (2) analysis of the critical period. The applications are performed using the best-currently-available estimates of flow data and penalty functions.