This study was employed to investigate the temporal variability and trend analysis of areal rainfall in the Muger subwatershed, Upper Blue Nile, Ethiopia. The study was run over the following procedures to handle the main objective: (1) determining the areal rainfall from gauged point rainfall using the Thiessen polygon method, (2) grouping the months in the season according to the study area, (3) evaluating the temporal dynamics of annual and seasonal areal rainfall using the coefficient of variation (CV), standard anomaly index (SAI), and precipitation concentration index (PCI), and (4) analyzing the trend of annual and seasonal areal rainfall using modified Mann–Kendall’s (modifiedmk) test in RStudio. Based on the temporal variability analysis, CV results depict that annual and summer areal rainfall had low variability with values of 13.43% and 13.7%, respectively. Winter and spring areal rainfall shows high variation with a CV value of 50.5% and 36%, respectively. According to the SAI output, around 70% of the considered year was in the normal condition of wetness. On the other hand, the seasonal (winter, spring, and summer) rainfall distribution of the study area shows strong irregularity distribution throughout the considered years as a result of PCI with a value of 57.5%. The trend of the areal rainfall was shown to be both increasing and decreasing. However, the trend was insignificant with a 10% confidence level.

中文翻译：

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埃塞俄比亚青尼罗河上游Muger小流域降雨时间动态及趋势分析

本研究用于调查埃塞俄比亚青尼罗河上游 Muger 子流域区域降雨量的时间变化和趋势分析。该研究按照以下程序进行，以实现主要目标：(1) 使用泰森多边形法根据测量点降雨量确定面积降雨量，(2) 根据研究区域对季节中的月份进行分组，(3) 评估使用变异系数（CV）、标准异常指数（SAI）和降水集中指数（PCI）来分析年和季节面积降雨量的时间动态，以及（4）使用修正的Mann-分析年和季节面积降雨量的趋势Kendall 在 RStudio 中的（modifiedmk）测试。根据时间变异性分析，CV结果表明，年和夏季面积降雨量的变异性较低，分别为13.43%和13.7%。冬季和春季面积降雨量变化较大，CV 值分别为 50.5% 和 36%。根据 SAI 的数据，所考虑年份中约 70% 的时间处于正常湿润状态。另一方面，由于 PCI 的影响，研究区的季节性（冬季、春季和夏季）降雨分布在整个考虑年份中表现出强烈的不规则性分布，其值为 57.5%。面积降雨量呈增加和减少趋势。然而，在 10% 的置信水平下，这一趋势并不显着。