In this research, the historical periods are divided into two periods: 1995-2005 and 2006-2016, so that these two periods, the changes of which are nearly 17% in rainfall, are examined. Two years 2008 and 2018 were selected to eva‎luate land use changes. Then, for the desired years, satellite images were prepared using Landsat 5 and 8 satellites and processed with ENVI 5/3 model and finally classified by support vector method. After that, using the SWAT model, two periods (1997-2005 and 2006-2016) were simulated under the land use of 2008 and 2018. After simulating the watershed, the runoff was calibrated and validated using the SUFI-2 algorithm in the SWAT-CUP software; In this way, the years 1995-2003 and 2006-2013 were selected for verification and the years 2005-2003 and 2014-2016 were selected for verification. One year for each period is considered as the warmup of the model, and after validation, the 2006-2016 period was simulated again with 2008 land use under calibrated parameters. Finally, the amount of blue water and green water has been investigated based on 3 situations (climate period 1995-2005 with land use in 2008 and climatic period 2006-2016 with land use in 2008 and 2018). The amount of precipitation in the study basin in the first period is 17% more than the second period of the eva‎luated model, and the amount of changes in the runoff entering the dam shows a decrease of 19%. Also, the flow of green water has decreased by 12%, and in the same way, the storage of green water has decreased by 5%. In 2018, land use in the urban class has increased by 20% and its amount has reached from 35.36 to 15.44 square kilometers; In the agricultural use class, the conditions are different and its use area has increased from 441 to 292 square kilometers, and in the Qala-Shahrokh sub-basin, it shows a huge increase in pasture due to more suitable rainfall in 2018, these changes cause a 5% decrease in water supply. at the basin level for the period of 2006-2016. These changes in green water have caused an increase in its components, which were 3.1 percent for green water flow and green water storage. After that, using the LARG-WGI model, rainfall and temperature data for climate stations for the future period of 2030-2050 were obtained based on RCP2/6, RCP4/5 and RCP8/5 scenarios. Using the SWAT model and assuming constant land use in 2018, blue and green water components were investigated. The results showed that the amount of runoff in Qala-Shahrokh basin has decreased by 15, 21 and 30% respectively for RCP2.6, RCP4.5 and RCP8.5 scenarios. The decrease occurred less in Eskandari station. The conducted investigations show that the changes of blue water are very sensitive to the amount of precipitation, and the components of green water were much less sensitive and showed very little dependence. In the following, by comparing the water volume of release scenarios, in the best case, that is, RCP2/6, the values were close to the third situation, and in the rest of the release scenarios, the blue water situation decreased and moved away from the third situation. One of the reasons for the decrease in runoff in the future period compared to the historical period in the Shahrokh Castle basin was the expected increase in temperature, which caused an increase in evaporation and transpiration; But in the rest of the sub-basins, evaporation and transpiration were relatively similar to the historical period.

آزاده احمدي

محمد حسين گل محمدي، رامتين معيني