| In the past few decades,most of the global river runoff has been significantly altered by climate change and human activities.The Kuye and Wuding rivers are located in the Yulin region of northern Shaanxi,where the unique natural geographical conditions make the study area ecologically fragile and highly dependent on water resources.This paper presents a comprehensive analysis of the basic characteristics of runoff from the two rivers based on hydrometeorological data,as well as information on water conservation areas and coal mining,the evolution of runoff sequences,and the quantitative calculation of the degree of influence of climatic factors and human activities on the changes in river runoff.The main results are as follows.(1)The intra-annual distribution of runoff in the Kuye River is extremely uneven,with runoff mainly concentrated from July to September,with a multi-year average runoff unevenness coefficient Cv of 0.83 and a complete deployment coefficient Cr of 0.33;the Wuding River is 0.35 and 0.14 respectively,with the Wuding River showing a more even intraannual distribution of runoff compared to the Kuye River,and with the reduction of runoff in the river,the intra-annual distribution of runoff in the two rivers tends to be more even.From the 1950s onwards,the overall trend of runoff volume relative to the multi-year average is abundant-flat-dry.(2)The runoff of the Kuye River from 1958 to 2020 shows a significant decreasing trend,and the future runoff of the river will continue to show a decreasing trend in general;the abrupt change points of the study period are 1979 and 1996,then it can be divided into three runoff sequences,i.e.the base period:1958 to 1979,the period influenced by human activities:1980 to 1996,1997 to 2020;there are mainly four main cycles in the study period,4a,9a,15a and 29a respectively.The runoff of the Wuding River also showed a significant decline from 1958 to 2020,and will continue to show a declining trend in the future;the abrupt change point of the study period is 1971 and 1988,which can be divided into three runoff sequences in turn,namely,the base period:1958 to 1971,the anthropogenic influence period:1972 to 1988,1989 to 2020;the study period is divided into three runoff sequences,namely,the base period:1958 to 1971,the anthropogenic influence period:1972 to 1988,and the anthropogenic influence period:1989 to 2020.The main periods of the study are 5a,16a and 32a.The runoff of both rivers is positively correlated with precipitation and negatively correlated with mean annual temperature.For example,from 1964 to 1972,there were significant resonance cycles of 2-4a between runoff and precipitation in the high energy area of the Cuyuno River,and from 1988 to 1998,there were significant resonance cycles of 2-5a between runoff and temperature in the high energy area of the Wuding River.(3)A stepwise regression model was used to obtain the significant factors influencing the runoff and the corresponding water reduction in each period of the two rivers,in which the significant factors influencing the runoff of the Kuye River from 1960 to 2015 were precipitation,temperature,the area of soil and water conservation measures and the amount of coal mining.Based on the baseline period(1960-1979),the water loss due to coal mining in 1980-1996 and 1997-2015 was 115.2×104m3,and 7821.2×104m3 respectively.The significant influencing factors of runoff from 1960 to 2015 in the Wuding River are precipitation,temperature and the area of soil and water conservation measures.Based on the base period(1960 to 1971)the runoff reduction caused by water conservation measures in the anthropogenic influence periods 1972 to 1988 and 1989 to 2015 are 23644.9×104m3 and 46599.1×104m3 respectively. |
