Abstract:

The concentrated distribution of precipitation is the main cause of flood disaster and hyper-concentrated flow. The study on the spatiotemporal of precipitation concentration and the discrimination of its main driving factors can provide support for regional water resource management and disaster warning. In this study, Jialing River Basin, the largest sediment-producing tributary in the upper reaches of the Yangtze River, was taken as the research area. Based on daily precipitation of 19 meteorological stations in the basin from 1954 to 2018, the annual average precipitation concentration (ACI) and long-term precipitation concentration (LCI) were calculated. The Mann-Kendall statistical test, Sen’s slope method and inverse distance weighted interpolation method were used to study the spatiotemporal pattern of precipitation concentration. Based on correlation analysis and random forest algorithm, the main driving factors were discussed. The results show that: (1) The spatial distribution of ACI and LCI of the Jialing River Basin shows a pattern of low in north and high in south. The southeast populated area of Jialing River Basin exhibits a higher precipitation concentration, indicating that extreme precipitation events will occur more frequently; while the northwest mountainous area of Jialing River Basin exhibits a lower precipitation concentration, indicating that extreme precipitation events will occur less frequently. (2) The value of precipitation concentration in Jialing River Basin ranges from 0.53 to 0.83, with large variation range; Of the 19 meteorological stations, 15 stations show an upward trend in precipitation concentration (8 stations show a significant upward trend), and 4 stations show a downward trend (2 stations show a non-significant downward trend). The trend difference of each station is also closely related to topographical and climate factors. (3) According to correlation analysis, it is found that there is a significant negative correlation between precipitation concentration and levation (p<0.01); The importance analysis results based on the random forest algorithm show that the climatic factor has the greatest impact on the precipitation concentration in the Jialing River Basin is the sunspot index, which is 17.24%~20.25%, followed by the ENSO index (MEI and SOI).