Relative importance of climatic and anthropogenic factors on runoff change at watershed scale

Climate change and anthropogenic activities, as two key important factors, cause remarkable changes in hydrological processes. Accordingly, in this study, the runoff coefficient index, a developed hydrologic regime method and the relative change approach were applied to distinguish the importance and contribution of each factor in runoff changes. Additionally, the double mass curve and Mann Kendall test were employed in the Middle Qomrood watershed located in the central part of Iran. For this purpose, the rainfall, runoff, temperature and evaporation statistics were utilized from 1990-2018. The proposed runoff coefficient indexes, MIP and MIR, with the values of 0.96 and 3.67 explain remarkable human effects in the region. Also, the developed hydrologic regime method, whose n-expressionry sumexpressiontion D-NP and n-expressionry sumexpressiontion D-NR values were 9.99 and 21.61, emphasized the importance of human activities. Moreover, the results of the relative change approach revealed that climate change and anthropogenic factors participation in hydrologic response during the study period were 21.25 and 78.75%, respectively. The results further specified that the contribution of direct and indirect anthropogenic factors was 70.51 and 8.24%, respectively. The Mann-Kendall test and double mass curve approach also verified that human activities caused the considerable change in runoff. The findings of this research will help decision maker for appropriate water resource management and environmental protection planning.