| Runoff is an important part of the water circulation system,and the runoff process plays an important role in the operation and replacement of the entire water resources system.Generally,runoff is mainly affected by climate and human activities,such as changes in the underlying surface.The study area in this paper is located in the arid region of northwest China,and the impact of runoff is more sensitive and fragile.This paper mainly studies and analyzes the runoff of Zamu River Basin from the aspects of climate and land use change.(1)Based on the serial data of runoff,precipitation,temperature,and potential evapotranspiration in the Zamu River Basin from 1961 to 2016,using intra-year and inter-generation(intergeneration)as the main research scales,using moving average,cumulative anomalies,Manne-Kendall Parameter testing and wavelet analysis are used to analyze and study the characteristics of trends,mutations and periodicity of various elements;the remote sensing images of the fourth-phase Zamu River Basin are corrected and interpreted to obtain the land use classification of the fourth-phase basin.Figures to statistically calculate the change characteristics of the area and land use degree of each land use type;use scatter plots,regression equations,correlation analysis and other methods to qualitatively describe the relationship between climate factors and land use type changes and runoff,etc.With the help of principles such as the double cumulative curve and its slope change,the impact of climate and land use changes on runoff can be distinguished,the contribution of each impact factor to runoff change can be quantified,and the evolution mechanism of runoff in the entire study sequence can be revealed in order to understand the research more deeply.Variation of regional runoff.(2)Variation characteristics of watershed air temperature,precipitation,potential evapotranspiration and runoff in time series are as follows: on an annual scale,monthly average temperature,monthly average precipitation,monthly average potential evapotranspiration,monthly average diameter The flow rate is a typical single-peak type change,and the maximum value of each hydro-meteorological element is July and August each year;the change of each season element also increases first and then decreases,and summer is the maximum period of each element,and winter It is the minimum value.The variation between summer and winter varies greatly and is obvious.The average value of each element from May to September accounts for more than 50% of the total total;on the decadal scale,the temperature,precipitation,and potential evapotranspiration of the basin Both the amount of output showed an upward trend,and the amount of runoff showed a downward trend,but the rising trend of temperature and potential evapotranspiration was significant,and the change of precipitation and runoff was not significant.The multi-year trends of various seasons are as follows: temperature,precipitation and potential evapotranspiration all increase in each season,while runoff decreases in spring and summer and increases in autumn and winter.The abrupt changes of various elements in the watershed are as follows: there is an obvious abrupt change point in the temperature series in 1996.The abrupt change points of the precipitation series are mainly concentrated in 2011-2015,but the abrupt change points are not significant.The potential evapotranspiration sequence has one and only one mutation point,located in 2004.There are also many mutation points in the sequence of runoff.After testing,it was found that the mutation effects were most obvious in 1966 and 1993.The abrupt change of runoff around 1966 was mainly caused by changes in precipitation,while the abrupt change of runoff around 1993 was mainly due to the influence of changes in potential evapotranspiration.(3)Based on GIS and RS technology,the fourth-phase remote sensing image of Zamu River Basin was geometrically corrected,spliced and tailored,fused and visually interpreted,etc.,and the land use classification standard and the actual situation of local nature and society were used to produce the study The four-stage land use classification maps of the district in 1986,2000,2006 and 2016,and then use Arc GIS and other software technologies to perform statistical analysis on the interpretation results to obtain the change characteristics such as area change and degree change,combined with correlation coefficients Investigating the correlation between land use change and runoff change,it is found that forest land and grassland have a decisive effect on runoff.Forest land and runoff change have a negative effect,and grassland has a positive effect on runoff change.(4)According to the cumulative anomaly curve,cumulative precipitationcumulative runoff curve and curve slope comparison method,the time series is divided into three stages,1961-1966 is selected as the natural stage,1967-1993 and 1994-2016 The year is the first stage and the second stage respectively,taking the natural stage as the base period,and distinguishing the contribution rate of the climate factor and the impact of land use on runoff changes one by one through the slope change.It is concluded that the temperature contribution rate is approximately-77% to 18.26%,the precipitation contribution rate is approximately 24% to 39%,and the land use change contribution rate is approximately 57% to 138%.In the first stage,climate and land use changes have a positive effect on runoff,but in the second stage,due to the negative temperature contribution,the total climate impact has a negative effect.Land use changes in the first and second stages The effect on runoff is positive. |
