Abrupt change of runoff and its major driving factors in Haihe River Catchment, China |
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| Authors: | Yonghui Yang Fei Tian |
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| Institution: | aKey Laboratory of Agricultural Water Resources, Hebei Key Laboratory of Agricultural Water-Saving, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang 050021, China;bGraduate University of Chinese Academy of Sciences, Beijing 100039, China |
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| Abstract: | Runoff in Haihe River Catchment of China is steadily declining due to climate change and human activity. Determining abrupt changes in runoff could enhance identification of the main driving factors for the sudden changes. In this study, the sequential Mann–Kendall test analysis is used to determine abrupt changes in runoff in eight sub-catchments of Haihe River Catchment, while trend analysis via the traditional Mann–Kendall test for the period 1960–1999 is used to identify the basic trend of precipitation and runoff. The results suggest an insignificant change in precipitation and a significant decline in runoff in five of the eight sub-catchments. For most of the sub-catchments, abrupt changes in runoff occurred in 1978–1985. Through correlation comparisons for precipitation and runoff for the periods prior to and after abrupt runoff changes, human activity, rather than climatic change, is identified as the main driving factor of runoff decline. It is also noted that abrupt decline in runoff was actually at the beginning of China’s 1978–1985 land reform. Given that the land reform motivated farmers to productively manage their reallocated lands, agricultural water use therefore increased. Hence percent agricultural land is analyzed in relation to land use/cover pattern for the late 1970s and early 1980s. The analysis shows that when cultivated farmland exceeds 25% of a sub-catchment area, an abrupt decline in runoff occurs. It is therefore concluded that high percent agricultural land and related agricultural water use are the most probable driving factors of runoff decline in the catchment. |
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| Keywords: | Runoff Precipitation Mann– Kendall test Sequential Mann– Kendall test Land use/land cover change |
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