Variation Characteristics And Influencing Factors Of Water Runoff In The Western Han Dynasty From 1960 To 2020

Water is a natural resource for our survival,but the impact of human activities and changes in climate play a direct or indirect role in the change of water runoff in the Western Han Dynasty.The research on water resources in the Western Han River Basin is of great significance for the rational development and utilization of water resources in the basin and the guarantee of water for domestic production and production in the future.The article selects the non-uniform coefficient method,the anomaly accumulation curve method,the trend coefficient method and the R/S analysis method to measure the Lixian Hydrological Station,Daqiao Hydrological Station and Tanjiaba(II)Hydrological Station in the Western Han River Basin from 1960 to 2020.Calculate the annual and monthly runoff data to explore its change characteristics and development trends;select land use dynamics and transformation matrix methods to explore the changing characteristics and degrees of land use structure in the basin;Precipitation characteristics,the characteristics and direction of changes in the underlying surface type,and the degree of influence of engineering construction on the water runoff in the Western Han Dynasty.Finally we can come to the following conclusions:(1)Affected by precipitation and evaporation,the runoff in the Western Han River Basin presents an uneven distribution throughout the year,with more in summer(JuneAugust)and less in winter(December-February).After the power station and the reconstruction of the irrigation area,the non-uniformity coefficient Cv,the concentration degree,and the concentration period all decreased,the annual distribution of runoff in the basin became more even,and the concentration period was advanced.(2)The runoff in the Western Han River Basin basically showed an increasing trend from 1960 to 1970,and the runoff from 1970 to 2020 basically showed a decreasing trend,showing a decreasing trend on the whole,and with the increase of the basin area,the runoff decreased.Intensified,showing a changing trend of alternating rich,flat,and dry years on an annual basis.The runoff data series of the Western Han River has a strong continuity,and in the future,the runoff of the Western Han River will continue to decrease.The runoff at Lixian Station,Daqiao Station,and Tanjiaba(II)Station in the Western Han River Basin are cyclically the same,with the first and second main periods being 44 a and 12 a.The years of the abrupt change points in the upper and middle reaches of the basin were 1970 and 1969,respectively.The earliest year of the abrupt change in the lower reaches was 1961.With the increase of the watershed area,the year of sudden change had a tendency to advance,and after 2000,the downward trend was significant.(3)The precipitation in the Western Han River Basin is uneven during the year,and the precipitation data series in the upper,middle,lower reaches and the whole basin show the characteristics of more in summer and less in winter.The precipitation in the upstream,downstream and the whole basin showed a decreasing trend as a whole,and the opposite in the middle reaches.The precipitation data series is very persistent.In the next period of time,the precipitation in the upper,lower reaches and the whole basin will continue to decrease,and the precipitation in the middle reaches will continue to increase.The first main period of precipitation in the upper,middle,lower reaches and the whole basin of the Western Han River is 42 a,57a,58 a,and 42 a,respectively.The abrupt change of precipitation in the upper,middle,lower reaches and the whole watershed of the Western Han River is not obvious.(4)The evaporation in the Western Han River Basin was uneven during the year,mainly concentrated in summer and autumn.The evaporation in the upper and lower reaches of the basin and the tributary Pingluo River showed an increasing trend,and the middle reaches showed a decreasing trend.The main stream evaporation data series were more persistent.In the next period,the evaporation in the upstream and downstream will continue to increase,and the evaporation in the middle reaches and tributary Pingluo Station will continue to decrease.The evaporation at Daqiao Station in the West Han River Basin has no periodicity during the study period.The first and second main periods of evaporation at Shunlixia Station,Pingluo Station and Tanjiaba(II)Station are 55 a and 31 a,55a and 44 a,56a and 35 a,the evaporation at Pingluo Station and Tanjiaba(II)Station has the third main cycle,27 a and 15 a,respectively.(5)The land use types in the upper reaches of the Western Han River Basin are mainly cultivated land and grassland,while the land use types in the middle reaches and downstream areas are mainly cultivated land,forestland and grassland.63%.From the late 1970 s to 2020,there was little change in land use types,and the conversion of land use types mainly occurred between cultivated land and grassland.(6)In different runoff change periods,the response degree of runoff to precipitation in each study interval is different.The response degree of upstream and downstream runoff to precipitation is high,and the response degree of midstream runoff to precipitation is low.Evaporation and runoff are negatively correlated,but the correlation is very weak.The linear correlation coefficient of the runoff accumulation in the whole basin is relatively high,the linear correlation of the accumulation curve is strong,the consistency of the runoff data sequence is good,and the systematic deviation is lower than other ranges.The systematic deviation of precipitation and evaporation in the whole basin is extremely low,and the consistency of precipitation and evaporation data series is good.(7)The runoff depth in the upper reaches of the Western Han River Basin increased due to the influence of precipitation,and decreased due to the influence of human activities,and human activities were the main reason for the decrease in runoff;the precipitation in the 3rd and 6th sections of the middle reaches was a positive influence,and the precipitation in other sections It is a negative impact,each interval is reduced due to the impact of human activities,and the main reason for the reduction of runoff is the impact of human activities;the precipitation in the third downstream interval is a positive impact,and the precipitation in other intervals is a negative impact.The interval decreased due to the influence of human activities,and the fourth and fifth intervals increased due to the influence of human activities.The main reason for the decrease in runoff before 1992 was the influence of human activities,and the main reason for the decrease in runoff after 1992 is a decrease in precipitation.