Faculty of Civil and Environmental Engineering, Jimma Institute of Technology, Jimma University, P.O. Box 378, Jimma, Ethiopia E-mail:
Faculty of Civil and Environmental Engineering, Jimma Institute of Technology, Jimma University, P.O. Box 378, Jimma, Ethiopia.
Water Sci Technol. 2024 Jul;90(1):75-102. doi: 10.2166/wst.2024.206. Epub 2024 Jun 15.
Evaluating how pollutant loads react to changes in land use/land cover (LULC) is a challenging task due to the intricate relationships among the many elements within a watershed. However, the difficulty in connecting LULC change and nonpoint source (NPS) pollution loads to streams may be lessened by combining hydrological modeling with geospatial tools and multivariate statistics. The objective of this study was to investigate the long-term effects of LULC change on NPS pollution loads in a highly human-dominated catchment, in central Ethiopia. In the study, hydrologic modeling was used to estimate the NPS parameters from multispectral Landsat images, and multivariate statistical techniques were then used to extract major LULC types that explain the variances of NPS loads between 1981 and 2020. The results demonstrated that there were human-induced LULC changes in the area, as the built-up and agricultural landscapes are rising (186.4% and 5.8%, respectively), and shrub and forest lands are decreasing (67.1% and 41%, respectively). As a result of these changes, the concentrations of nitrate (NO), total P, total N, organic N, and organic P loads were increased by 69.41, 19.83, 18.45, 18.88, and 24.05%, respectively. Reductions in natural vegetation, as well as agriculture intensification, are the major contributors to the NPS pollutant losses to surface water sources. The result also revealed that pollution nutrients are strongly related to deforestation and agricultural land expansion. Proper adaptation strategies should be implemented to minimize the negative impact of LULC changes in the area.
评估污染物负荷如何响应土地利用/土地覆盖（LULC）变化是一项具有挑战性的任务，因为流域内有许多要素之间存在错综复杂的关系。然而，通过将水文模型与地理空间工具和多元统计相结合，将 LULC 变化与非点源（NPS）污染负荷与溪流联系起来的难度可能会降低。本研究的目的是调查土地利用变化对埃塞俄比亚中部一个高度人为主导流域中 NPS 污染负荷的长期影响。在研究中，利用水文模型从多光谱 Landsat 图像估算 NPS 参数，然后利用多元统计技术提取主要的 LULC 类型，这些类型解释了 1981 年至 2020 年 NPS 负荷变化的差异。结果表明，该地区存在人为引起的土地利用变化，因为建成区和农业景观在增加（分别为 186.4%和 5.8%），而灌木和林地在减少（分别为 67.1%和 41%）。由于这些变化，硝酸盐（NO）、总磷、总氮、有机氮和有机磷负荷的浓度分别增加了 69.41%、19.83%、18.45%、18.88%和 24.05%。自然植被的减少以及农业集约化是导致 NPS 污染物向地表水水源流失的主要原因。研究结果还表明，污染养分与森林砍伐和农业土地扩张密切相关。应实施适当的适应策略，以最大限度地减少该地区土地利用变化的负面影响。
