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

Abstract

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.

Characterizing and Modeling Seasonality in Extreme Rainfall

“…Additionally, the latter provides support to within-year operation of water resources systems, design rainfall estimation (Efstratiadis et al, 2014;Golian et al, 2010), and probabilistic assessment of extreme events occurring in a given season. Nowadays, extreme rainfall seasonality also prompts renewed scientific interest as a field of trend analyses (Dhakal et al, 2015;Ntegeka & Willems, 2008;Tye et al, 2016;Wu & Qian, 2017).…”

Groundwater Chemistry Regulated by Hydrochemical Processes and Geological Structures: A Case Study in Tongchuan, China

“…The study area belongs to the warm semi-arid to semi-humid climate and has hot, rainy summers but cold and dry winters [19]. The average annual rainfall is 537.86 mm (more than 50% of which occurs from July-September) [20], and the annual evaporation is 1445.65 mm. The mean minimum and maximum temperatures are 3 and 23 • C, respectively.…”

“…The (Ca 2+ + Mg 2+ ) − (HCO 3 − + SO 4 2− ) equation means that the cations Ca and Mg were corrected by omitting the influences by other processes (e.g., carbonate or silicate weathering), whereas the (Na + + K + ) − Cl − equation means that the cations K and Na were from sources other than their respective chlorides [49]. If ion exchange is the dominant process in the system, the samples should form a line with a slope of −1 [16,20,42,49]. Figure 6e shows that cluster 1 and cluster 2 samples have a slope of −1, indicating cation exchange influences the groundwater chemistry of these samples, and cluster 3 has a slope of −0.6, indicating that cation exchange shows less influence on the water chemistry in cluster 3 than it does in the other clusters.…”

Combination of modified Mann‐Kendall method and Şen innovative trend analysis

“…Mann‐Kendall (MK) trend test is used for trend detection in hydrometeorological records such as temperature, rainfall, evaporation, evapotranspiration, streamflow, and water quality . In addition, Şen_ITA is used by many researchers, which gives successful results to identify trend component in a given time series such as temperature, precipitation, water quality and relative humidity, solar radiation, streamflow, water level, evapotranspiration in the literature.…”

“…precipitation, [16][17][18][19] water quality and relative humidity, 20 solar radiation, 21 streamflow, 22 water level, 23 evapotranspiration 24,25 in the literature.…”