System dynamics applied to water management in lakes*

Water withdrawal and changes in hydrologic fluxes have lowered the level of Urmia Lake in Iran, adversely impacting its ecosystem. The continued lowering of the Urmia Lake water level would put Iran's most important aquatic ecosystem in danger of extinction. Therefore, there is an urgent need for management of water withdrawals and for reduction of water use in upstream dams and rivers to halt its continuing decline and allow storage recovery. The Urmia Lake basin was herein modelled with system dynamics (SD) to assess the effects of modifying reservoir operation and water use management on the sustainability of Urmia Lake storage. The model performance was evaluated with the root mean square error (RMSE) and the correlation coefficient (R-2). The results show that SD with RMSE = 18.0 (10(6) m(3)) and R-2 = 0.952 is accurate in simulating Urmia Lake storage. Evaluation of the impacts of several scenarios of agricultural water use on lake storage indicates that reductions in the agricultural sector appear inevitable to restore the water balance of Urmia Lake.