Research on the variation trends of precipitation and runoff in the Pearl River Basin based on innovative trend analysis method

Abstract

[Objective] Precipitation and runoff are the key elements of the hydrological cycle. Studying the trend variations of precipitation and runoff, especially further exploring changes in their relationship, is of great significance for understanding climate change, water resources management, and ecological protection. [Methods] Based on a long series of precipitation and runoff data from 1956 to 2019, the innovative trend analysis method was used to analyze the variation trends of precipitation, runoff, and runoff coefficient at different spatiotemporal scales in the Pearl River Basin. [Results] The result showed that:(1) the overall annual precipitation in the Pearl River Basin showed a downward trend, with changes in low-value categories declining by more than 5%, indicating an increased likelihood of drought in the Pearl River Basin, and the change trend of annual runoff was consistent with that of precipitation. Across different sub-basins, the West River and East River showed significant downward trends, while the North River showed an upward trend.(2) From a seasonal perspective, spring and autumn precipitation in the Pearl River Basin showed a significant downward trend, while summer and winter precipitation showed an upward trend. The spring high precipitation values and all types of autumn precipitation showed a downward trend of more than 5%, and the summer high precipitation values and winter low-to-median precipitation showed an upward trend of more than 5%. The variation trends of annual runoff in spring, autumn, and winter were consistent with precipitation, but were opposite in summer.(3) The runoff coefficient showed a significant downward trend, especially in high values. Preliminary analysis suggested that the decrease in runoff coefficient was related to the increase of evapotranspiration, changes in vegetation coverage, and the regulation and storage of water engineering.(4) The consistency rate between the innovative trend analysis method and the traditional Mann-Kendall method was 70% for trend type and 22% for significance. [Conclusion] Spatiotemporal variation characteristics of precipitation, runoff, and runoff coefficient in the Pearl River Basin: From a temporal perspective, the annual precipitation and runoff in the Pearl River Basin show an overall declining trend, with a significant decrease in the runoff coefficient. From a spatial perspective, the precipitation and runoff in the West River and East River exhibit a noticeable downward trend, while the North River shows an upward trend. The innovative trend analysis method, compared to the Mann-Kendall method, demonstrates significant differences in trend significance testing.

Keywords

innovative trend analysis / climate change / precipitation and runoff / runoff coefficient / spatiotemporal variation characteristics / Pearl River Basin