The definition of drought is very controversial due to its multi-dimensional impact and slow propagation in onset and end. Predicting the accurate occurrence of drought remains a challenging task for researchers. The study focused on hydrological and meteorological drought monitoring and trend analysis in the Abbay river basin, using the streamflow drought index (SDI), standardized precipitation index (SPI), and reconnaissance drought index (RDI), respectively, to fill this research gap. The study also looked into the interrelationships between the two drought indicators. The SDI, SPI, and RDI were calculated using long-term streamflow, precipitation, and temperature data collected from 1973 to 2014. The data were collected from eight streamflow stations and fifteen meteorological gauge stations. DrinC software (Drought Indices Calculator) was used to calculate the SDI, SPI, and RDI values. The result from meteorological drought using SPI12 and RDI12 shows that 1975, 1981, 1984, 1986, 1991, 1994, and 2010 were extreme drought years, whereas 1983, 1984, 2001, and 2010 were the most extreme hydrological drought years based on the SDI12 result. Except for Bahir Dar and Gondar, a severe drought occurs at least once a decade in all stations considered in this study. In general, the SPI, RDI, and SDI results indicated that the study area was exposed to the most prolonged severe and extreme drought from 1981 to 1991. The findings of this study also demonstrated that the occurrence of hydrometeorological droughts in the Abbay river basin has a positive correlation at long time scales of 6 and 12 months. The trend analysis using the Mann–Kendall test implied that there was a significant meteorological drought trend in two stations (Debre Berhan and Fiche) at SPI12 and RDI12 time scale, but for the remaining thirteen stations, there is no trend in all time scales. The hydrological drought trend analysis in the basin on a seasonal (SDI3) and yearly (SDI12) time scale also revealed that three streamflow stations have a positive trend (Kessie, Gummera, and Border). This implies that water resource management is still a vital tool for the sustainable development of the Abbay river basin in the future.

中文翻译：

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埃塞俄比亚阿拜河流域水文气象干旱监测及趋势分析

干旱的定义因其多维影响和始末传播缓慢而备受争议。预测干旱的准确发生对于研究人员来说仍然是一项具有挑战性的任务。该研究重点关注阿拜河流域的水文气象干旱监测和趋势分析，分别使用径流干旱指数（SDI）、标准化降水指数（SPI）和勘测干旱指数（RDI）来填补这一研究空白。该研究还调查了两个干旱指标之间的相互关系。SDI、SPI 和 RDI 是使用 1973 年至 2014 年收集的长期流量、降水和温度数据计算得出的。这些数据是从八个流量站和十五个气象站收集的。DrinC 软件（干旱指数计算器）用于计算 SDI、SPI 和 RDI 值。基于SPI12和RDI12的气象干旱结果表明，1975、1981、1984、1986、1991、1994和2010年是极端干旱年份，而1983、1984、2001和2010年是基于SDI12的最极端水文干旱年份结果。除 Bahir Dar 和 Gondar 外，本研究中考虑的所有站点每十年至少发生一次严重干旱。总的来说，SPI、RDI 和 SDI 结果表明，研究区在 1981 年至 1991 年遭受了最长的严重和极端干旱。本研究结果还表明，阿拜河流域水文气象干旱的发生已经在 6 个月和 12 个月的长期尺度上呈正相关。使用 Mann-Kendall 检验的趋势分析表明，两个站点（Debre Berhan 和 Fiche）在 SPI12 和 RDI12 时间尺度上有显着的气象干旱趋势，但对于其余 13 个站点，在所有时间尺度上都没有趋势。流域季节性 (SDI3) 和年度 (SDI12) 时间尺度的水文干旱趋势分析还显示，三个流量站（Kessie、Gummera 和 Border）呈正趋势。这意味着水资源管理仍然是未来阿拜河流域可持续发展的重要工具。流域季节性 (SDI3) 和年度 (SDI12) 时间尺度的水文干旱趋势分析还显示，三个流量站（Kessie、Gummera 和 Border）呈正趋势。这意味着水资源管理仍然是未来阿拜河流域可持续发展的重要工具。流域季节性 (SDI3) 和年度 (SDI12) 时间尺度的水文干旱趋势分析还显示，三个流量站（Kessie、Gummera 和 Border）呈正趋势。这意味着水资源管理仍然是未来阿拜河流域可持续发展的重要工具。