Assessing the impacts of different management scenarios on the environmental sustainability of Gharachai watershed using the WEAP

Water resources development projects have many environmental effects, the most important of which are changing the natural regime of the river and reducing the downstream flow. The use of hydrological models allows for sustainable planning in water resources management. The Qarachai River Basin in the Salt Lake Basin has been affected by human activities in recent years. In the present study, the hydrological behavior of Qarachai catchment was modeled using 21WEAP software. The model was developed, calibrated and validated for a 25-year statistical period (1993 to 2017). To calibrate the model, the observed discharge values of Qarachai River located at Asgarabad station (catchment outlet) were calculated with computational values using Nash-Sutcliffe coefficient index. A 13-year statistical period (from 1993 to 2006) was considered for model calibration. The Nash-Sutcliffe coefficient for the calibration period was obtained 0.86. An 11-year statistical period (2006-2007) was considered for validation. The value of Nash-Sutcliffe coefficient for the validation period was obtained 0.74. These results indicate the good efficiency of the WEAP model in simulating the hydrological behavior of the Qarachai catchment. After analyzing five management scenarios, finally a combined scenario with a reliability index above 95% for each consumption sector as well as meeting the environmental needs was recognized as the top scenario. The results of the research indicate that with the implementation of this scenario, the downward trend of the aquifer compared to the current situation will be greatly adjusted and exit from the critical state will be possible by applying appropriate management measures.