Spatiotemporal trends and variability of rainfall across agro-ecologies in East Guji Zone, Southeast Ethiopia

PLOS Climate Pub Date : 2024-03-21 DOI:10.1371/journal.pclm.0000361

Menbere Sahilu, Solomon Tekalign, Yimer Mohammed, Tegegne Sishaw, Haji Kedir, Solomon Asfaw

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Abstract

Distribution and trends of rainfall reveal spatial and temporal variability that have a paramount effect on the life and livelihood of small-holder farmers. This study aimed to analyze spatial variability and temporal trends of rainfall distribution across the three Agro-Ecological Zones (AEZs) of East Guji. Time series gridded daily rainfall data (1990–2020) were collected from the Ethiopian Meteorological Institution. Different descriptive statistics, trend tests: Man Kendal and Sen’s slope estimator, Inverse Distance Weighted Index and Precipitation Concentration Index (PCI) was used in the study. The finding demonstrated that altitude and rainfall decrease as one advances from the western (highland) to the eastern (lowland) direction in the study area where the highest rainfall was recorded in Solemo (highland) and the least in Negele (lowland).The study showed that as altitude increases annual rainfall also increases and rainfall variability decreases. Similarly the mean length of the growing season declines as one advance from the highlands to the lowlands. The PCI of the lowlands, midlands, and highlands AEZs was 19%, 17%, and 12% respectively. The PCI showed that those highlands had moderately concentrated rainfall but both lowlands, and midlands, had an irregular distribution of rainfall. The Coefficient of Variation (CV) indicated that highland areas had moderate variability in rainfall in all seasons except winter. In contrast, the low and midlands had shown high variability of rainfall (>30%) in all seasons. From a seasonal perspective, both CV and PCI revealed that the winter season showed more variability than others. Moreover, a significant increasing trend of annual rainfall was observed in the highlands AEZs (Bore 15.3mm/year and Solemo14.6mm/year), lowland AEZs (Chembe 10.9mm/year, Dawa 8mm/year and Bitata 7.8mm/year) as well as midland AEZs (Kercha 14.5mm/year) at a significant level of 5%. Therefore, strategies should be designed to use additional water resources for irrigation; and provide short-cycle grown and drought-resistant crops in the rest of the midlands and lowlands AEZs.

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埃塞俄比亚东南部东古吉区不同农业生态区降雨的时空趋势和变异性

降雨量的分布和趋势揭示了对小农生活和生计具有重要影响的空间和时间变异性。本研究旨在分析东古吉三个农业生态区（AEZ）降雨分布的空间变异性和时间趋势。从埃塞俄比亚气象研究所收集了时间序列网格化日降雨量数据（1990-2020 年）。进行了不同的描述性统计和趋势检验：研究中使用了 Man Kendal 和 Sen 的斜率估计器、反距离加权指数和降水集中指数（PCI）。研究结果表明，在研究地区，随着从西部（高原）向东部（低地）推进，海拔高度和降雨量都在下降，其中 Solemo（高原）降雨量最高，Negele（低地）降雨量最低。同样，随着从高地向低地推进，生长季节的平均长度也在缩短。低地、中地和高地农业经济区的 PCI 分别为 19%、17% 和 12%。PCI 显示，高地的降雨量适度集中，但低地和中地的降雨量分布不规则。变异系数（CV）表明，除冬季外，高原地区在所有季节的降雨量都有中等程度的变异。相比之下，低地和中部地区在所有季节的降雨量变化都很大（大于 30%）。从季节角度看，CV 和 PCI 均显示冬季降雨量的变异性高于其他季节。此外，在高地农业经济区（Bore 15.3 毫米/年和 Solemo 14.6 毫米/年）、低地农业经济区（Chembe 10.9 毫米/年、Dawa 8 毫米/年和 Bitata 7.8 毫米/年）以及中地农业经济区（Kercha 14.5 毫米/年），年降雨量呈显著增加趋势，显著水平为 5%。因此，应制定战略，利用更多的水资源进行灌溉；并在其余的中部和低地农业经济区提供短周期种植和抗旱作物。

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PLOS Climate

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