Climate change and Human activities are the two main factors in changing the hydrological cycle processes trend. Which as their own cause change in the spatial and temporal distribution of available water as well as river flows. Therefore, it is very important to determine the contribution of climate change and human activities to river flow changes to select policies and suitable strategies that are consistent with the management and planning of regional water resources. In this study, four approaches have been used to differentiate the effects of human activities and climate change on the Zayandehrud dam inflow fluctuations. For this purpose, firstly using the Man-Kendall method, analyzed the annual trend of climatic (precipitation and evapotrairation potential) and flow data. The inflow data trend at all stations was statistically significant with a decreasing value of the recent period runoff. The result shows a decreasing trend in three precipitation stations which are statistically significant and for potential evapotrairation data, except one station (Zayandehrud Dam), the significant and increasing trend. Pettit test was used to calculate the breakpoint runoff hydrological data, the test results for two stations of Eskandari and Mandarjan indicate 1996 as hydrological breakpoint and 2007 for QaleShahrokh Station. Since it is necessary to select a specific year for a breakpoint in the simulation, this calculation for evapotrairation data was also done. Given that the result was the vicinity of 1996 this year were chosen. Then, using three methods including climate elasticity, Multi regression and least squares support vector machine model (LS-SVM), the effects were determined. To validate the results, the hydrologic simulation method was used. in this regard, the basin was calibrated and validated in the normal period using the semi-distributed SWAT model. Finally, the contribution of climate change impacts and human activities to reducing runoff in the sub-basin was calculated. The results indicate a 16 to 48 percent share of climate change and a 51 to 84 percent share of human activities in reducing runoff to the Zayanderroud Dam. To diminution the contribution of human activities in changing runoff, three scenarios were defined including maintaining and replacing other cultures cultivation of wheat and barley with wheat and barley, the maintenance of wheat and barley crops and the replacement of other crops with potatoes and increased irrigation efficiency. In all three scenarios, the inflow of the Zayandehrud dam increased and the optimal scenario for all stations was first scenario. Keywords : separating the impacts, Climate Elasticity, Multi Regression, Hydrologic Simulation, LS-SVM Model, SWAT Model.
