Water And Sediment Changes In The Upper Zuli River And Their Response To Precipitation And Soil And Water Conservation Measures

In the context of climate change,studying the impact of precipitation and soil and water conservation measures on watershed sediment changes can provide a scientific basis for the rational development and protection of watershed water resources,soil erosion control,land use adjustment,and regional economic development.In this paper,the upstream of the Zuli River,a first-level tributary of the Yellow River,is used as the research area.Based on the runoff,sediment data and precipitation data of the Huining Hydrological Station and the data of soil and water conservation measures in the basin from 1957 to 2016,the M-K mutation test and Morlet wavelet method are used to analyze The annual precipitation,runoff and sediment transport trends,catastrophic years and periodic characteristics were analyzed.The regression analysis method and the double-cumulative curve method were used to study the annual rainfall,soil and water conservation measures changes on the river basin runoff and sediment transport in stages.Impact and contribution rate.The main research conclusions are as follows:(1)The annual precipitation shows a trend of insignificant reduction in fluctuations during the study period,,the annual precipitation showed a big difference,and there is an obvious"abundant-dry"periodic change between years,with an average annual precipitation of 406.4mm.From 1957 to 1974,the precipitation showed a significant increase trend,of which the change from 1963 to 1968 reached a significant level;from 1975 to 1990,there was no obvious change in precipitation;from 1991 to 2016,the precipitation showed an insignificant decrease trend.The mutation occurred in 1991.There are 4~8 a,11~15 a and 16~32 a periodic changes in precipitation,there are 5 a,8 a,22 a and 27 a 4 major cycles,and there are 3 a,5 a and 13 a,18 a average change period.(2)The annual runoff showed a declining trend of fluctuations during the study period,,the annual runoff showed a big difference,and there was an obvious"abundant-dry"periodic change between years,with an average annual runoff of 12.274 million m~3.From 1957 to 1974,the runoff showed an insignificant increasing trend;from 1975 to 1999,the runoff showed a significant decreasing trend,of which the change from 1993 to 1999 reached a significant level;from 2000 to 2016,the runoff showed a significant decreasing trend,Flows changed suddenly in2000.There are 3~7 a,8~12 a,and 14~32 a periodic changes in annual runoff,with 3 main periods of 4 a,9 a,and 27 a,and 3 a,6 a,and 18 a average changes period.(3)The annual sediment transport volume showed a significant decrease in fluctuation during the study period,,the annual sediment transport showed a big difference,and the annual sediment transport showed obvious"more-less"cyclical change,with an annual sediment transport of 3.676 million t.From 1957 to 1974,the sediment transport volume showed an insignificant increasing trend;from 1975 to 2002,the sediment transport volume showed a significant decreasing trend,of which the change from 1996 to 2000 reached a significant level;from 2003 to 2016,the sediment transport volume decreased Trend,the amount of sediment transport suddenly changed in 2003.There are 3 to 7 a,8 to 12 a,and 14 to 32 a periodic changes in annual sediment transport.There are 4 main cycles of 4 a,6 a,8 a,and 27 a,and there are 3 a,4 a,and 5 a,18 a average change period.(4)The amount of soil and water conservation measures showed a gradual increase during the study period.The area of soil and water conservation measures increased from 300 hm~2 in1957 to 59,300 hm~2 in 2016,of which terraced area increased by 23,300 hm~2,afforestation area increased by 14,900 hm~2,grass planting area increased by 15,100 hm~2,and closed area increased2,100 hm~2,the degree of soil erosion control reached 60.31%.(5)The trend synergy of the response of runoff and sediment transport to precipitation changes gradually weakened,and the trend synergy of response to changes in soil and water conservation measures gradually increased.The contribution rate of precipitation to runoff and sediment transport is 25.81%and 29.80%respectively,the contribution rates of soil and water conservation measures to runoff and sediment transport is 74.19%and 70.20%respectively.Change in soil and water conservation measures is the main reason for the reduction in runoff and sediment transport in the basin.