Analysis of Runoff Change and Its Influencing Factors of Miju River Based on Morlet Wavelet Analysis

Since 2011,the annual runoff of the Miju River Basin has been relatively small for 8 consecutive years,and the Miju River is the largest major river into the Erhai Sea,with runoff area and natural runoff accounting for more than 40% of the total flow of the Erhai Sea.Therefore,analyzing the variation characteristics of the annual runoff of Miju River is of great significance to the study of the total water flowing into Erhai Sea.Based on the monitoring data such as flow,precipitation and evaporation of the Liancheng hydrologic station in the basin from 1954 to 2018,this paper studies the change law of runoff cycle and its influencing factors by wavelet analysis.The results show that:The natural annual runoff of Miju River basin in the nearly 65 a decreases with time,with an average annual runoff decrease of 14.35 million m³ per 10 a;The annual runoff is featured with periodic changes of about 9 a,14 a,19 a,and 54 a,which greatly affects the trend of abundance and dryness of annual runoff;There are multiple time scales nesting between the four-season runoff and annual runoff,and the first main period of the four-season and annual runoff is about 54 a;The change trend and fluctuation cycle of annual precipitation and annual runoff of Miju River are similar,with a positive correlation;The annual evaporation has various impact on the annual runoff;The influence of water consumption on runoff in the Miju River Basin is increasing,the conditions of the lower surface are changing more and more,and the relationship between precipitation and runoff varies accordingly,which is one of the main reasons for the significant decrease of runoff in the basin compared with that under same precipitation in the past.