Attribution analysis of runoff variations in the upper reaches of Hutuo River Basin

The upper reaches of the Hutuo River basin was selected to study the driving forces of runoff evolution for sustainable utilization of water resources under changing environment. Quantitative analysis of the contribution rates of climate change and human activities to runoff change was presented, using 4 elasticity methods based on Budyko framework and SWAT model. Annual precipitation, annual runoff in the upper reaches of Hutuo River from 1961 to 2016 showed downward trend and significant downward trend respectively, while evapotranspiration showed significant upward trend, drought trend of the basin was marked. Elasticity-based methods showed that climate change accounted for 49.62%-61.67% of total decrease in runoff, human activities accounted for 38.33%-50.38%. SWAT simulation showed that climate change accounted for 84.42%, human activities accounted for 15.58%. Such differences emerged because landscape parameter in Budyko equations reflects not only human activities, but also impact of climate change. Therefore climate change played a dominant role in the decline in runoff in the upper reaches of Hutuo River basin, but impact of human activities on runoff is increasing. The specific reason for decrease in runoff caused by human activities was not land use change, but rather excessive development and utilization of water resources due to economic and population growth.