Dynamic simulation of generic archetype of upstream sefid rud basin and river inflow under influence of dams

Introduction: available water resources and their management are very important in preserving and sustaining the development plans of a country, along with providing foodstuffs. Meanwhile, the main tributaries and flooded rivers of a country play a vital role. There are also very important rivers in Iran, one of which is Ghezel Ozan. This river originates in Kurdistan province and it reaches Gilan province after it passes through downstream provinces and joins Sefid-Rud river after which it is called Qezel Ozen of Sefid-Rud river and enters the great dam of Sefid-Rud. In the meantime, considering small details of the area, modeling will provide a faster and more accurate investigation so that managers can use it. In this regard, there are two views, dynamic and linear. In this research, the mechanistic view was used as a decision support system due to the available feedback, holistic thinking, and the possibility of using the model. Then the problems of the region were evaluated by identifying generic archetypes.
Materials and methods: The current research has dealt with the dynamic simulation of the surface water resources allocation in upstream Sefid-Rud basin during the years 1990 to 2019 in two annual and monthly scales. During 1990 to 2011 when the dams had not yet started to operate, simulation was conducted by considering about 30 intervals in the mainstream of the rivers and tributaries of Kurdistan province, part of Zanjan province, and a small area of Hamadan province precipitation, discharge and ground waters as well as all agricultural products, domestic and industrial amounts as input.
Results and discussion: The annual scale of the model structure, with MAE, RMSE, and R2 scales of 0.098, 0.087, and 0.980, respectively, confirmed the accuracy and precision of the model along with the test of the limit conditions that are specific to the dynamic system. Due to the construction of dams, since 2010, monthly simulations were carried out in two sections, before and after the dams' operation. Before the operation of the dams, the values of MAE, RMSE, and R2 were equal to 0.052, 0.103, and 0.940, respectively, confirming the high efficiency of the model. From 2011 to 2019, modeling was defined so as during the first 6 months of water year, water withdrawal was done from the river and during the second 6 months it was done from the dam. All the specifications of the dams along with the needs of the region were simulated in all intervals on a monthly scale. In the meantime, according to the dynamic simulation, the feedback and causal loops formed by them formed patterns that corresponded to the generic archetypes of the region. With the start of the dams, the escalation archetype, limits to growth archetype, and fixes that fail archetype were activated and the increase in water withdrawal was observed in all intervals, whether with the construction of the dam or not.
The results showed that despite the drop of aquifers to an average amount of 30 meters in the whole period and 6.35 meters after the construction of dams, in addition to a 90% reduction in discharges, there was an increase in water withdrawal and despite the severe reduction of water resources, the area under cultivation in dealing with escalation archetype has increased by four times, and following the limits to growth archetype, there has been a very sharp decrease to about 3 times. On average, in the region, the area under cultivation has increased by 2.8 times, at the highest value by 4 times and at the lowest value by 1.6 times. The results indicate that, dam construction led to inappropriate exploitation in the region.