An Integrated Approach for Partitioning the Effect of Climate Change and Human Activities on Surface Runoff

Climate change and human activities have been identified as the two main reasons for the change in runoff. To better understand the factors causing runoff change, this paper develops an integrated approach which combined the elasticity coefficient approach (including a non-parametric model and six Budyko framework based models) and the hydrological modelling approach (using SIMHYD models) for partitioning the impacts of climate change and human activities on surface runoff. The Guanzhong River Basin(GRB), which is the sub-basin of the Wei River basin in China is chosen as the study area. In this study, trends in runoff, rainfall and potential evapotranspiration (PET) from 1958 to 2008 are analyzed using the Mann-Kendall test and change-points in the annual runoff from 1958 to 2008 are sought using the Fu formula, Mann-Kendall test and double mass curve. The calibrated and validated rainfall-runoff model SIMHYD is used to simulate the runoff in the GRB during 1958–2008. Seven different methods are used to calculate the elasticity coefficient and then the elasticity coefficient methods are used to evaluate the contribution of climate change and human activities. Combining all these results, the contribution of climate change and human activities to runoff change is 34.1 ~ 47.3 and 52.7 ~ 65.9 %, respectively. The study provides scientific foundation for understanding the causes of water resources decrease and significant information for water resources management under the influence of climate change and human activities.