Hydrological Response to Human Activities and Climate Change in the Ghaleh-Shahrokh Watershed

Determining the relative contributions of human activities and climate change to variations of runoff in basin is very important for sustainable management of water resources. In this study, seven methods were used to determine these relative contributions in the Ghaleh-Shahrokh watershed as the main upper catchment of Zayandeh-Roud River. These seven methods can be divided into two main categories, including empirical methods and elasticity-based methods. At first, Pettitt method was used to determine undisturbed and disturb periods of the runoff in the watershed and then relative contributions of climate change and human activities were determined by using the different methods. The results of this study show that the human activities play a dominant role in the reduction of runoff in the Ghaleh-Shahrokh catchment. According to the empirical and the elasticity-based methods, human activities account for 64.5 % (47 to 82%) and 76 % (70 to 89 %) of the total runoff decrease, respectively. Also, 35.5 % and 24 % of the total decrease in runoff in the catchment was due to climate change effects according to the empirical and elasticity-based methods, respectively. Generally, it can be concluded that the elasticity-based methods are better than the empirical methods in determining the contributions of human activities and climate change to runoff variations, because they take into account the evapotranspiration addition to rainfall and runoff.