This book discusses how the importance of river flow-sustained ecosystems for local communities can be quantified for the purpose of balancing water supply and demand in Integrated Water Resources Management. Due to the development of water resources, for example through the construction of reservoirs, the natural flow regime of rivers is altered which results in changes in the river and floodplain ecosystem. Environmental flows describe the river flow regime necessary to protect the river ecosystem. The importance of this ecosystem for peoples' food, income, health or other purposes, are referred to in this work as the human well-being values of environmental flows. The publication provides an approach to quantify the relationship between river flows, the river ecosystem and human well-being values and discusses the application of this approach in two case studies, in Bangladesh and in Iran. The approach proved to structure the assessment of well-being values and to yield additional useful information that can contribute to the enhancement of social equity in Integrated Water Resources Management.