Evaluation of solutions to supply part of the environmental requirements of Lake Urmia using MODSIM and Analytic Hierarchy Process (AHP)

As a result of droughts and human interventions, the Urmia Lake basin has faced increasing unallowable withdrawal of water resources and environmental requirements share. Over the past two decades, a series of natural and human factors have gradually changed the water balance of Lake Urmia. In addition, decreases in precipitation have been the main reason for the gap between water resources and increasing water consumption in the basin, especially in the agricultural sector. In order to deal with the Urmia Lake catastrophe, a working group was formed for the Urmia Lake restoration. The working group planned and proposed solutions to reach the ecological level of the lake in three stages within 10 years through in-basin water supply and inter-basin water transfer programs. The present research, while investigating the solutions for providing the environmental water requirement of Lake Urmia using the Analytic Hierarchy Process (AHP) method, changes in the water volume of Lake Urmia in the scenarios of water transfer from the surface flow of each entering river in the lake in the years of high intensity severe to mild drought, the implementation of the approvals of the national working group to restore Urmia Lake, including a 40% reduction in agricultural consumption from the sources of dams and other rivers without dams, releasing water from dams in non-agricultural seasons, transferring water from urban wastewater and finally transferring water between the Zab basin has quantitatively been evaluated using the MODSIM simulation model. This research will help to predict the amount of transferable water in drought, normal, and drought conditions and to plan the water accounting of the Urmia catchment. 

The watershed of Lake Urmia, located in the northwest of Iran, with an area of 51,876 square kilometers, is one of the six main watersheds of the country, which is located between the provinces of West Azerbaijan, East Azerbaijan, and Kurdistan. In terms of its territorial location, the catchment area of the Zab Kochak river is in the western part of the international border with Iraq and in the catchment area of the Western Border River basin. A significant part of the Zab watershed (source of water transfer) is located outside the country and in Iraq. The route of water transfer between the basins of the Zab basin is from the place of two dams, Silweh and Kaniseeb, which after entering the Godarchai river will eventually enter the Urmia lake water body. The different solutions from the working group’s approval have been selected for developing six scenarios. Then, the Scenarios have been evaluated by the MODSIM model and AHP analysis method. The scenarios are including reducing agricultural expenses from dams in operation, saving by reducing agricultural expenses from other rivers, transferring water between basins, transferring effluent to Lake Urmia, releasing water from dams in operation to Lake Urmia. A hierarchical structure was developed with the aim of evaluating solutions to save Lake Urmia through internal sources and transfer water sources. In this structure, there are four criteria of climate, consumption, economic-social, and environmental status. Sub-criteria of drought, surface water extraction from rivers, extraction from dam sources, extraction from groundwater resources, development of agricultural lands, and ensuring the sustainability of river flow. and providing solutions for inter-basin water transfer, a 40% reduction of agricultural water consumption from surface water sources of rivers and dams, wastewater transfer, and a 40% reduction of agricultural water consumption from underground water sources in Expert Choice software, were analyzed. 

In order to evaluate the effectiveness of the defined scenarios, the simulation model was implemented for future conditions during the next 10 or 15 water years for different scenarios. The results show that the implementation of scenarios 4 and 6, will bring the largest increase in the volume of lake water, of course, with the occurrence of precipitation and proper input. Regarding the results of scenario 1 and the sameness of its results in two periods of 10 and 15 years, it can be stated because in the definition of the scenario, it is a dry year and the amount of evaporation of the lake water is more than the amount of input into the lake. There has been no increase in the lake's water volume for several consecutive years. Also, the results show that in wet and dry years, if the maximum transfer flow scenario is implemented, we will not have a flow from the Zab river to the downstream side, and it will not be accepted from the hydrodiplomacy point of view for the neighboring country in terms of influencing the use of the Dukan dam. Therefore, water diplomacy solutions are needed to reduce environmental threats. Therefore, the issue of transferring water from the Zab basin to Lake Urmia cannot be considered guaranteed in the long term due to the impossibility of reducing the outflow of water from the country to zero. 

In conclusion, in order to evaluate all scenarios to satisfy the environmental needs of Lake Urmia shows that the protection of the lake requires correcting the mistakes of the path traveled in the current and past years, and preferably with a 40% reduction in agricultural consumption from dams and other rivers, groundwater in the basin is the main supplier of Urmia Lake. Inter-basin water transfer is the next priority because the source catchment is able to transfer water in the face of droughts due to the reduction of runoff and related challenges as well as its negative economic and social effects. It will not be as much as predicted and included in the program (600 million cubic meters per year). In addition to that, water diplomacy is necessary in terms of impacting downstream transboundary uses and reducing environmental threats. The results of this research and the high costs of water supply requirements, in parallel with the investigation of controversial options and costs of inter-basin water transfer projects, macro-management of water resources towards demand and consumption management and water saving programs and the modification of water consumption patterns and the legality of the behavior of water users from within the catchment area of Lake Urmia should be low-cost, sustainable and reliable solutions.