Development of a rational management philosophy for existing reservoirs is being stimulated by the rapid exploitation throughout the world of dam sites which are economically and ecologically viable. A nonlinear, stochastic mathematical programming algorithm is used to maximise profit from the operation of a reservoir over a finite time period, namely an annual hydrologic cycle, taking account of water used for domestic, industrial, irrigation, low-flow augmentation, and power demands, and of losses due to seepage and evaporation.