For economic modeling in the Ganges Basin, an estimate of the water demand in the Ganges Dependent Area (GDA) in Bangladesh is required. This paper outlines a method for estimating this water demand. The proposed method is based on the integration of hydrological and hydraulic process models with economic models. In Bangladesh, a variety of mathematical models are currently used to estimate the impacts on Bangladesh’s water resources system for different: upstream flow conditions, local hydrologic situations, Bay of Bengal circumstances, etc. The models include basin level hydrological models, 1-dimensional and 2-dimensional hydrodynamic models, morphological model, salinity model, Bay of Bengal model, etc. The first step in the proposed method it to use these models to simulate a range of hydrologic and hydraulic scenarios in the GDA in Bangladesh. The next step involves using the outputs from these physical process models as inputs to economic models that estimate the economic benefits (and costs) in the GDA. These economic models will focus on different sectors that can potentially benefit from additional freshwater flows to the region, e.g. irrigated agriculture, open-water and capture fisheries, navigation, ecosystem services (particularly the Sundarbans), dredging of river channels, water logging in polder areas, water supply, etc. For example, currently there is practically no flow into the Gorai River, a key river in the GDA, from the Ganges during the months of January to May. As a result, there is increased river salinity and sedimentation in the southwest region. Additional flows will not only allow increased agriculture production and improve water supply options but also reduce the costs of regular dredging of key rivers in the region. These estimated benefits represent economic water demands for the GDA in Bangladesh.