Analyzing the variability of sediment yield: A case study from paired watersheds in the Upper Blue Nile basin, Ethiopia
Analyzing the variability of sediment yield: A case study from paired watersheds in the Upper Blue Nile basin, Ethiopia
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DOI：
10.1016/j.geomorph.2017.12.020
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发表时间：
2018-02-15
期刊：
影响因子：
3.9
通讯作者：
Yibeltal, Mesenbet
中科院分区：
文献类型：
--
作者：
Ebabu, Kindiye;Tsunekawa, Atsushi;Yibeltal, Mesenbet
流域尺度的空间和时间变化的产沙量（SY）的知识，需要设计侵蚀控制战略，特别是在最严重的侵蚀地区。本研究的目的是提供这方面的知识，埃塞俄比亚的潮湿的热带高地使用Akusity和Kasiry成对的流域在古德部分的上青尼罗河流域。在2014年和2015年雨季期间，使用自动流量传感器、手动标尺和深度综合沉积物采样器监测了流量和悬浮泥沙浓度数据。利用经验流量泥沙曲线计算了每个雨季不同部分的SY。测得的平均日沉积物浓度在不同年份和流域之间差异很大（Kasiri在2014年为0.51 g L-1，2015年为0.92 g L-1，Akusity在2014年为1.04 g L-1，2015年为2.20 g L-1）。无论降雨模式如何，随着雨季的到来，两个地点的沉积物浓度都有所下降，原因是沉积物供应枯竭，植被覆盖增加导致水流的输送能力有限。2014年和2015年，Kasiry的雨季SYs分别为7.6 t ha（-1）和27.2 t ha（-1），而Akusity的SYs分别为25.7 t ha（-1）和71.2 t ha（-1）。2015年的数值大得多，部分原因是降雨量增加和更大的洪峰流量事件。峰流量事件的大小和时间是SY数量和变异性的主要决定因素。因此，特定地点的评估，这样的事件是至关重要的，以揭示在热带高原环境中的小流域SY动态。(C)2018爱思唯尔B. V.保留所有权利。
Improved knowledge of watershed-scale spatial and temporal variability of sediment yields (SY) is needed to design erosion control strategies, particularly in the most severely eroded areas. The present study was conducted to provide this knowledge for the humid tropical highlands of Ethiopia using the Akusity and Kasiry paired watersheds in the Guder portion of the Upper Blue Nile basin. Discharge and suspended sediment concentration data were monitored during the rainy season of 2014 and 2015 using automatic flow stage sensors, manual staff gauges and a depth-integrated sediment sampler. The SY was calculated using empirical discharge sediment curves for different parts of each rainy season. The measured mean daily sediment concentration differed greatly between years and watersheds (0.51 g L-1 in 2014 and 0.92 g L-1 in 2015 for Kasiry, and 1.04 g L-1 in 2014 and 2.20 g L-1 in 2015 for Akusity). Sediment concentrations at both sites decreased as the rainy season progressed, regardless of the rainfall pattern, owing to depletion of the sediment supply and limited transport capacity of the flows caused by increased vegetation cover. Rainy season SYs for Kasiry were 7.6 t ha(-1) in 2014 and 27.2 t ha(-1) in 2015, while in Akusity SYs were 25.7 t ha(-1) in 2014 and 71.2 t ha(-1) in 2015. The much larger values in 2015 can be partly explained by increased rainfall and larger peak flow events. The magnitude and timing of peak flow events are major determinants of the amount and variability of SYs. Thus, site-specific assessment of such events is crucial to reveal SY dynamics of small watersheds in tropical highland environments. (C) 2018 Elsevier B.V. All rights reserved.