A modeling framework for sustainable water resources management

A prototype modeling framework for quantitative analysis of sustainable water resources management at the river basin scale is developed and applied to the Syr Darya River basin in Central Asia to analyze long-term water resource system sustainability. The research problem is specified as long-term, sustainable water resources management in river basins that are characterized by (semi)-arid climate, a heavy dependence on irrigated agriculture, and severe environmental degradation in the form of water and soil salinity. Sustainable water management is defined here as ensuring a long-term, stable and flexible water supply capacity to meet crop water demands, as well as growing municipal and industrial water demands, at the same time as keeping a stable relationship between irrigation practices and their associated environmental consequences. For this research, an innovative systems approach has been developed to model and analyze sustainability issues related to water resources management. The core of this modeling framework consists of an intra-year, short-term optimization model and an inter-year, long-term, dynamic model that combines simulation and optimization. In the intra-year model, essential hydrologic, agronomic, economic, and institutional relationships are integrated into a coherent analytical framework at the river basin scale to reflect the interdisciplinary nature of water resources problems. The inter-year model includes long-term changes and uncertainties in both water supply and demand, and incorporates prescribed sustainability principles for river basin system performance control. Relations between short-term irrigation practices and their long-term economic and environmental consequences are modeled and controlled in the inter-year modeling framework. The intra-year, or short-term, model is applied to the Syr Darya River basin to explore case-specific in-depth hydrologic-agronomic-economic-institutional relationships. This application shows the power of this type of integrated optimization model. Moreover, the application of the long-term modeling framework to the case study area shows the effectiveness of this tool for sustainability analysis in this region. Three approaches based on decomposition analysis and newly developed genetic algorithms for solving highly complex water resources management models that are large, nonconvex, and nonlinear are presented and applied. The short-term model, which is a large and nonlinear model, is solved by a "piece-by-piece" approach based on model decomposition. A new genetic algorithm - linear programming approach is used to solve the long-term model. Throughout the study, both the feasibility and the effectiveness of incorporating the philosophy of sustainability into traditional water resources management modeling are addressed. It is argued that system modeling techniques, if well supported by relevant empirical studies, and if sufficient data are available, can promote the understanding of sustainability in water resources research, a concept of utmost importance that will strongly influence future research in water resources management.