New Integrated Hydrologic Approach for the Assessment of Rivers Environmental Flows Into the Urmia Lake

Abstract

In the conducted researches recently the greatest focus has been on the environmental water supplement of rivers individually and independently. However, in closed basins leading to lakes and wetlands, a comprehensive and integrated view of all rivers in the basin is required simultaneously. This has affected Lake Urmia, which is the second largest saltwater lake in the world. This lake has been in danger of drying up in recent years as a result of not allocating the required environmental flow due to the increase in water resources consumption in the agricultural sector and climate change. In this study, a method derived from the flow duration curve (FDC) shifting method is presented in addition to the possibility of providing the environmental flow of rivers leading to the lake that can make the least amount of change in the hydrological characteristics of rivers to provide the volume of required water by the ecosystem of lakes or downstream wetlands. This method is based on daily data of hydrometric stations and, unlike the conventional method, which presents the results on a monthly basis, it can calculate the amount of environmental requirement of rivers in real-time according to the upstream inlet of the river. This method has been used in the Urmia Lake basin and according to the results, it can provide the environmental requirement of lake by allocating 70.5% of the annual flow of rivers and save the lake and the ecosystem of the region from the current critical conditions.