System Dynamics Analysis for Managing Iran's Zayandeh-Rud River Basin

Within river basins different social, economic, political and physical subsystems interact. When making decisions, policy makers should be aware of such interactions as any new policy will affect more than one subsystem. To determine the adequacy of a specific management policy, an integrated study is needed of a complicated water management system in the basin considering major physical, social, economic and political aspects. The Zayandeh-Rud river basin, in central Iran with a semi-arid climate and large agricultural, industrial and domestic water uses, is an example of a complicated watershed system where the lack of complete knowledge about all the interacting subsystems has led to failure of the policy makers in addressing the water shortage in the basin. Although water shortages occur fairly soon after completion of each new water source, transbasin water diversion is still the major policy of water planners to address ongoing shortages. System dynamics provides a unique framework for integrating the disparate physical, socio-economic and political systems important to watershed management. This approach is used to comprehend the interactions of different drivers of the problem and to convey the experiences, lessons learned, and perceptions gained during the model development process. A simulation model, built based on causal loop diagrams of the problem, shows that transbasin diversion is not the best and only solution to the problem. The results of the model for different scenarios suggest that various options of demand management and population control can be more effective in addressing the water crisis of the basin when combined with transbasin water diversions, increasing water storage capacity and controlling of groundwater withdrawal.