Joint water quantity-quality management in a biofuel production area-integrated economic-hydrologic modeling analysis

Water management in the Pirapama River Basin in northeastern Brazil is affected by both water quantity and water quality constraints. The region is known for significant sugarcane-based ethanol production-which is the key to the Brazilian economy and expected to grow dramatically under recent changes in climate and energy policies. Sugarcane production in the region goes hand in hand with controlled fertirrigation practices with potentially significant adverse impacts on the environment. To assess sustainable water allocation in the basin, an integrated hydrologic-economic basin model is adapted to study both water quantity and quality aspects. The model results show that incorporating water quality aspects into water allocation decisions leads to a substantial reduction in application of vinasse to sugarcane fields. Embedding highly nonlinear water quality constraints in a basin optimization model is demonstrated to be an effective tool to address the water management problems in rapidly developing biofuel areas of Brazil and elsewhere.