Abstract: This paper describes a ratio of power revenue losses to ecological benefits for assessment of the losses in the power generation revenues of a reservoir, considering the constraint of different ecological base flows in its medium and long-term optimal operation. This ratio parameter can be used for examining the impact of ecological base flow on the revenue and exploring the possibility of increasing ecological base flow in practice. In a case study of the Laluo hydro-junction in Tibet, we calculated the ecological base flows of its lower reach using a hydrologic method, and developed new schemes for optimal reservoir scheduling under the constraint of irrigation and ecological water demands. In the new schemes the ecological base flow was increased by various amounts, and the ratios of power revenue loss to ecological benefit calculated. Results show that in the Laluo case, it is feasible to increase the ecological base flow and this measure can minimize the relative losses in generation benefits per unit volume of ecological water.