Large-scale bioenergy production will affect the hydrologic cycle in multiple ways, including changes in canopy interception, evapotranspiration, infiltration, and the quantity and quality of surface runoff and groundwater recharge. As such, the water footprints of bioenergy sources vary significantly by type of feedstock, soil characteristics, cultivation practices, and hydro-climatic regime. Furthermore, water management implications of bioenergy production depend on existing land use, relative water availability, and competing water uses at a watershed scale. This paper reviews previous research on the water resource impacts of bioenergy production-from plot-scale hydrologic and nutrient cycling impacts to watershed and regional scale hydro-economic systems relationships. Primary gaps in knowledge that hinder policy development for integrated management of water-bioenergy systems are highlighted. Four case studies in the Americas are analyzed to illustrate relevant spatial and temporal scales for impact assessment, along with unique aspects of biofuel production compared to other agroforestry systems, such as energy-related conflicts and tradeoffs. Based on the case studies, the potential benefits of integrated resource management are assessed, as is the need for further case-specific research.

ResumoO artigo identifica os custos de oportunidade da alocação de efluentes nas áreas plantadas de cana, distantes mais de 2 Km da agroindústria JB, nos meses de safra em que isso não ocorre. Esses custos são obtidos por meio dos valores marginais das variáveis de decisão, provenientes do problema de maximização de benefícios econômicos, resolvido por meio do General Algebraic Modeling System (GAMS) e da análise do dual do problema linearizado. Além disso, simulam-se diferentes coeficientes para os custos de transporte e de tratamento de efluentes para verificação dos efeitos sobre sua alocação e os benefícios associados à mesma. Desta forma, pode-se subsidiar a identificação de taxas e/ou subsídios que favoreçam a alocação dos efluentes em áreas plantadas de cana mais distantes das agroindústrias, proporcionando não só ganhos de produtividade mais disseminados, como também o respeito aos limites de qualidade do rio. Palavras-Chave efluentes, fertirrigação, custo de oportunidade AbstractThis paper identifies the opportunity costs in effluent allocation over sugarcane crop acres located more than 2Km away from the agroindustry plant JB, during the harvest season. The optimization problem described herein explains why these opportunity costs are usually missed. Actually, these costs derive from the marginal values associated to the decision-making variables concerning an economic benefit maximization problem resolved using the General Algebraic Modeling System (GAMS) and from the dual analysis of the linearized problem therein. Besides, different effluent transportation and effluent treatment cost coefficients were considered in simulating possible impacts and benefits regarding effluent allocation. This approach supports the optimal definition of charging and/or subsidizing schemes best suited to allocate effluents over sugarcane crops located farther away from hub agroindustry plants, not just for more disseminated productivity gains, but also for best compliance with river water quality constraints.