Integration of water quantity and quality in strategic river basin planning

The integration of surface water quantity and quality objectives within the framework of a decision-support tool is presented in an application to the 12,400-km(2) Piracicaba River Basin in the state of Sao Paulo, Brazil. Emphasis is given to simulation-based assessment of strategic planning alternatives through the combined use of water allocation (MODSIM) and water quality routing (QUAL2E-UNCAS) models. Uncertainty from temporal and spatial variability and inadequate data associated with model parameters is addressed. Performance measures for water allocation include total reliability, total vulnerability, and total resiliency. Water quality performance measures are stream standard compliance reliability, water quality index, spatial uniformity of water quality, and temporal uniformity of water quality. These measures are used to evaluate and compare alternatives in light of multiple planning objectives. Six management alternatives, combining various reservoir release policies with differing levels of wastewater treatment, are refined through systematic simulation to a final plan recommended for detailed consideration. The recommended plan results in predicted performance that dependably meets transbasin diversion to the city of Sao Paulo while maintaining high intrabasin water allocation performance.