Policymakers at national, state and local levels are charged with the efficient and sustainable use of water resources of the São Francisco River basin, and also to promote economic growth and reduce poverty within the basin. To date, policymakers lack scientific evidence on the consequences for growth, poverty alleviation or environmental sustainability of alternative uses of water resources. To address this key knowledge gap we will develop and use a spatially distributed description of the economic and hydrologic sub-systems, as well as their linkages, and quantify the field to region to basin water and poverty impacts of alternative water policy decisions in the São Francisco Basin.
Basin-wide descriptive analysis of water availability and use, agriculture and poverty will set the stage for predictive modeling at the basin, sub-basin and plot levels. At basin level, an aggregate mass balance hydrology model will be developed and linked to município-level economic models to predict the effects of alternative water management strategies and policies on product mix, production technology and area under plow, and the consequences of these agricultural choices for poverty, water productivity, and flows for environmental and other purposes. The model will generate estimates on an annual basis, with the potential to predict agriculture and water use/availability into the future. At sub-basin level an integrated model will be constructed from the field to the watershed scale, consisting of a hydrologic model linked to an agricultural production model. This hydrologic model is a spatially distributed, three-dimensional, variably-saturated flow and transport model, with full reactive salt chemistry capabilities. Given initial conditions on surface water allocation, and soil, surface water, and groundwater quality and quantity, an economic model will predict the types and spatial extent of agricultural activities on an annual basis and produce spatially distributed information on: cropping patterns, water applications, groundwater pumping, irrigation efficiencies, crop yields and revenues from agricultural activities. The output from the economic model is subsequently used by the hydrologic model to simulate the impacts of these management decisions on the natural system including environmental water use. The agricultural production model in turn is updated annually by the hydrologic model to account for changes in soil quality, and groundwater quality and quantity (and hence, water costs). At plot level, land use system (LUS) analysis will assess the impacts on small-scale and other agriculturalists of changes in water availability, water costs and water quality. All models will be used to assess the effects of water management interventions, with special attention paid to effects on poverty and water productivity.