Innovative trend analysis of annual and seasonal rainfall and extreme values in Shaanxi, China, since the 1950s

Rainfall is a primary component of the water cycle, and its variability is associated with drought and flood events. This study investigates the trends in annual and seasonal rainfall at 14 rainfall stations in Shaanxi Province, China, using an innovative trend analysis (ITA), Mann-Kendall test and linear regression analysis. Moreover, using ITA, annual rainfall is analysed for different rainfall intensities, and seasonal rainfall is analysed for extreme values. The results show non-uniform trends in rainfall intensities on a regional and seasonal scale. Annual rainfall shows a significant decreasing trend in the Wei River Basin and north of the Loess Plateau. Overall, the trend is reinforced with the increase of rainfall intensity. A few stations show significant trends in seasonal rainfall. Spring rainfall is the major contributor to the decline in annual rainfall. Heavy rainfall (more than 90th percentile) in summer exhibits a marked downward trend mainly in the basin, which makes it possible for flooding to abate along the Wei River. Light rainfall (less than 10th percentile) shows a prevailing increasing trend in summer, but a decreasing trend in other seasons. From north to south, the seasonal trends become clearer and stronger. In terms of management, more attention should be paid to autumn droughts in the Wei River Basin. A quantitative measurement of a trend for ITA is proposed. Comparison of the three methods endorses the ITA method. Moreover, the ITA shows many advantages, such as graphical results and for observing sub-trends. It is hoped that this study can provide support for water resources planning, for coping with droughts and floods and for future development of the ITA method.