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Watershed hydrological responses to changes in land use and land cover, and management practices at Hare watershed, Ethiopia

机译：埃塞俄比亚黑尔流域对土地利用和土地覆被变化以及管理实践的流域水文响应

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摘要

This study investigates hydrological responses to changes in land use, land cover and management practices at Hare River watershed, Southern Rift Valley Lakes Basin, Ethiopia. It addresses methods that are required to better characterize impacts of land use and cover and climate change scenarios and understand the upstream-downstream linkages with respect to irrigation water allocation. Understanding how the changes in land use and cover influence streamflow and subsequently optimization of available water resources utilization can enhance the ability of planners, practitioners, researchers and farmers to formulate and implement sound policies to minimize undesirable future impacts and devise management alternatives. Three land use and cover maps were developed using aerial photographs and satellite image through visual interpretation of the aerial photographs and supervised classification of the satellite image. The rates of land use and land cover changes were identified for two periods at watershed and sub-watershed levels. Two physical-based, semi-distributed hydrological models, SWAT2005/ArcSWAT and HSPF, were utilized to simulate hydrological responses to land use and climatic changes. Streamflow data at the outlet of the watershed was utilized to analyze seasonal stream flow variability due to land use and land cover changes. The performances of the models have been evaluated through sensitivity analysis, calibration, validation and uncertainty analysis. Consequently, impacts of hypothetical land use and climate change scenarios were developed to analyze their impacts on downstream water users. Eventually, based on the results these scenario analyses a new optimal irrigation water allocation tool was developed to allocate available water resources among competing irrigation sites.The results of the land use and land cover change analysis identified that farmlands and settlements class has expanded during the past four decades. Detailed impacts of these changes were analyzed employing the SWAT2005. Sensitivity analysis using the SWAT2005 model has pointed out some crucial parameters that control the surface and subsurface hydrological processes of the studied watershed. Consequently, results of the models performances assessment illustrated that both SWAT2005 and HSPF have resulted acceptable outputs with some efforts of acquiring data in areas where there is limited available data. However, the SWAT2005 model performs slightly better than HSPF for monthly and seasonal streamflow analysis. As a result, streamflow variability during the dry and wet seasons was further analysed using this model based on pre-identified scenarios. Furthermore, uncertainty analyses were performed and discussed using ParaSol, SUNGLASSES, SUFI-2 and GLUE methods. On the other hand, results from the climate change scenario analysis using GCM for the period of 2010-2099 showed that an increase in future average annual precipitation and average temperature when compared to the baseline period. Similarly, analysis made on intervention of small scale irrigation in the upper and middle reach of the watershed resulted in substantial decrease in mean monthly discharge during the dry season, while increased discharge during the wet season. Consequently, an optimal tool was developed to allocate scarce water resources among three upstream and downstream demand sites with a prime objective of achieving equitable resources utilization while maintaining acceptable economic efficiency and environmental sustainability. The analysis revealed that a substantial volume of water can be saved through deficit irrigation principles. It is also noted that, in the face of intense competition among irrigation water users where there is a significant water shortage throughout a watershed, equitable and efficient utilization of water resources has always remained a social goal. The developed tool can be used in other watersheds too by decision makers and planners where there exist irrigation water allocation problems between competing upstream and downstream irrigation sites. However, it needs simulation outputs from SWAT2005 and needs to specify the exact sub-watersheds where the irrigation sites are located. In order to utilize outputs from other models, the tool needs some modification in the algorithm (visual basic) specifically on the declaration of the input files. Generally, the results highlighted that use of an integrated simulation-optimization approach has a paramount importance to investigate impacts of land use and cover and climate change on hydrological regime and consequently allocate limited available water resource in an equitable manner among competing sites.
机译：这项研究调查了埃塞俄比亚南部纵谷流域哈里河流域对土地利用，土地覆盖和管理实践的变化的水文响应。它提出了一些方法，这些方法可以更好地表征土地利用，覆盖和气候变化情景的影响，并了解与灌溉水分配有关的上游与下游之间的联系。了解土地利用和覆盖面的变化如何影响水流，进而优化可用水资源利用，可以增强规划者，从业人员，研究人员和农民制定和实施合理政策的能力，以最大程度地减少未来的不良影响并设计管理方案。通过航空照片和卫星图像的视觉解释和对卫星图像的监督分类，开发了三幅土地利用和覆盖图。在分水岭和分水岭水平上确定了两个时期的土地利用和土地覆被变化率。利用两个基于物理的半分布式水文模型，SWAT2005 / ArcSWAT和HSPF，来模拟对土地利用和气候变化的水文响应。流域出口处的流量数据被用于分析由于土地利用和土地覆盖变化而引起的季节性流量变化。该模型的性能已通过敏感性分析，校准，验证和不确定性分析进行了评估。因此，开发了假设的土地利用和气候变化情景的影响，以分析其对下游用水者的影响。最终，基于这些情景分析结果，开发了一种新的最佳灌溉水分配工具，可在竞争的灌溉地点之间分配可用水资源。土地利用和土地覆盖变化分析的结果表明，过去的耕地和居民点类别有所增加四十年。使用SWAT2005分析了这些更改的详细影响。使用SWAT2005模型进行的敏感性分析指出了控制所研究流域地表和地下水文过程的一些关键参数。因此，模型性能评估的结果表明，SWAT2005和HSPF都已经取得了可接受的输出，并且付出了一些努力来获取可用数据有限的区域中的数据。但是，SWAT2005模型在月度和季节性流量分析方面的性能略好于HSPF。结果，基于预先确定的情景，使用该模型进一步分析了干燥季节和潮湿季节的流量变化。此外，使用ParaSol，SUNGLASSES，SUFI-2和GLUE方法进行了不确定性分析并进行了讨论。另一方面，使用GCM进行的2010-2099年气候变化情景分析结果表明，与基准期相比，未来的年平均降水量和平均温度都有所增加。同样，对流域上游和中游小规模灌溉进行干预的分析结果表明，干旱季节的平均月排放量显着减少，而潮湿季节的排放量增加。因此，开发了一种最佳工具，可在三个上游和下游需求点之间分配稀缺的水资源，其主要目标是实现合理的资源利用，同时保持可接受的经济效率和环境可持续性。分析表明，通过亏缺灌溉原则可以节省大量的水。还应指出的是，面对灌溉用水用户之间的激烈竞争，在流域中严重缺水的情况下，公平，有效地利用水资源一直是社会目标。决策者和计划者也可以在其他流域中使用开发的工具，在这些流域中，上游和下游灌溉站点之间存在灌溉水分配问题。但是，它需要SWAT2005的模拟输出，并且需要指定灌溉点所在的确切子流域。为了利用其他模型的输出，该工具需要对算法（Visual Basic）进行一些修改，尤其是在声明输入文件时。总体而言，结果突出表明，使用综合的模拟优化方法对于调查土地使用和覆盖以及气候变化对水文状况的影响以及因此在竞争站点之间公平分配有限的可用水资源至关重要。

著录项

  • 作者

    Mengistu Kassa Tadele;

  • 作者单位
  • 年度 2009
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  • 原文格式 PDF
  • 正文语种 eng
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