*Article* **Base Flow Variation and Attribution Analysis Based on the Budyko Theory in the Weihe River Basin**

**Zheng Mu 1,†, Guanpeng Liu 1,†, Shuai Lin <sup>1</sup> , Jingjing Fan 1,2,\*, Tianling Qin 2,\* , Yunyun Li <sup>3</sup> , Yao Cheng <sup>1</sup> and Bin Zhou <sup>1</sup>**


**Abstract:** The composition and change of runoff are closely related to climate change and human activities. To design effective watershed water resources management measures, there is a need for a clear understanding of the impact of climate change and human activities on baseflow and surface runoff. The purpose of this essay is to quantify their impact on the annual total stream flow, surface runoff, and base flow in the Weihe River Basin (WRB) using a two-stage annual precipitation partitioning method, wherein the surface runoff and base flow are separated from the measured total flow by using a one-parameter digital filter method for which the common filter parameter value is 0.925. The stream flow records were split into two periods: 1960–1970 (pre-change period) and 1971–2005 (post-change period) based on the hydrological breakpoints detected. We found that climate change and human activities have different impacts on base flow and surface runoff. We attributed the decrease in surface runoff due to climate change accounting for 76–78%, while we determined that human activities were responsible to the decrease in base flow accounting for 59–73% of the total observed change. We concluded that both climate change and human beings contributed to the hydrologic change through different hydrological processes: climate change dominated the surface runoff change, while human influences controlled the base flow change. To achieve the expected goals of ecological restoration, appropriate measures must be taken by watershed management in the WRB to mitigate the likely impacts of climate change on water hydrology.

**Keywords:** climate change; human activities; base flow; surface runoff; Weihe River Basin
