The Didesa catchment, which is the second largest subbasin of the Abay basin, significantly contributes to the Blue Nile’s outflow. Understanding the dynamics of water availability under the changing climate in such a basin assists in the proper planning of land use and other development activities. This study presents changes in climatic elements such as rainfall, temperature, and evapotranspiration using observation data and regional climate models (RCMs) under two representative concentration pathways (RCPs) for three future periods. We use a calibrated hydrological model to further assess climate change’s effects on streamflow. We select three RCMs and their ensemble’s mean by evaluating their performance with respect to observations. We apply the modified Mann–Kendall test to detect trends in each dataset. The result shows that annual mean maximum and minimum temperatures increase in the catchment for the 2021–2040, 2041–2070, and 2071–2100 periods as compared to baseline (1989–2018) under both RCP4.5 and RCP8.5 scenarios. Annual mean maximum temperature and potential evapotranspiration experienced a significant decreasing trend during the year from 1989 to 2018. Furthermore, there was an increasing trend in annual rainfall from 1989 to 2018, which could be related to the cooling of sea surface temperature over the equatorial Pacific. We detect an increasing trend in temperature in both scenarios and all periods; however, no clear trend pattern is found in rainfall. The result from hydrological model simulations reveals that the mean monthly streamflow slightly increases in the winter season while it decreases during the main rainy season. Further study of detailed weather systems, which affect the subbasin’s climate, is recommended.

中文翻译：

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模拟气候变化对埃塞俄比亚阿拜盆地迪德萨流域水流的影响

迪德萨流域是阿拜盆地的第二大子流域，对青尼罗河的流出量做出了重大贡献。了解此类流域气候变化下水资源供应的动态有助于正确规划土地利用和其他开发活动。本研究使用观测数据和区域气候模型（RCM）在未来三个时期的两个代表性浓度路径（RCP）下呈现降雨、温度和蒸散量等气候要素的变化。我们使用校准的水文模型来进一步评估气候变化对水流的影响。我们通过评估它们在观测方面的表现来选择三个 RCM 及其集合的平均值。我们应用修改后的曼-肯德尔检验来检测每个数据集中的趋势。结果表明，在RCP4.5和RCP8.5情景下，与基线（1989-2018年）相比，2021-2040年、2041-2070年和2071-2100年流域年平均最高和最低气温均有所增加。1989-2018年年平均最高气温和潜在蒸散量均呈显着下降趋势，而1989-2018年年降雨量呈增加趋势，可能与赤道太平洋海表温度变冷有关。我们检测到两种场景和所有时期的温度都有上升趋势；然而，降雨量没有发现明显的趋势模式。水文模型模拟结果表明，冬季月平均径流量略有增加，而主雨季则有所减少。