Graduate School of Science and Engineering, Soka University, Hachioji, Tokyo, Japan.
College of Agriculture and Environmental Science, Bahir Dar University, Bahir Dar, Ethiopia.
Environ Sci Pollut Res Int. 2024 Jul;31(33):45929-45953. doi: 10.1007/s11356-024-34212-x. Epub 2024 Jul 9.
Urbanization, agriculture, and climate change affect water quality and water hyacinth growth in lakes. This study examines the spatiotemporal variability of lake surface water temperature, turbidity, and chlorophyll-a (Chl-a) and their association with water hyacinth biomass in Lake Tana. MODIS Land/ Lake surface water temperature (LSWT), Sentinel 2 MSI Imagery, and in-situ water quality data were used. Validation results revealed strong positive correlations between MODIS LSWT and on-site measured water temperature (R = 0.90), in-situ turbidity and normalized difference turbidity index (NDTI) (R = 0.92), and in-situ Chl-a and normalized difference chlorophyll index (NDCI) (R = 0.84). LSWT trends varied across the lake, with increasing trends in the northeastern, northwestern, and southwestern regions and decreasing trends in the western, southern, and central areas (2001-2022). The spatial average LSWT trend decreased significantly in pre-rainy (0.01 ℃/year), rainy (0.02 ℃/year), and post-rainy seasons (0.01℃/year) but increased non-significantly in the dry season (0.00 ℃/year) (2001-2022, P < 0.05). Spatial average turbidity decreased significantly in all seasons, except in the pre-rainy season (2016-2022). Likewise, spatial average Chl-a decreased significantly in pre-rainy and rainy seasons, whereas it showed a non-significant increasing trend in the dry and post-rainy seasons (2016-2022). Water hyacinth biomass was positively correlated with LSWT (R = 0.18) but negatively with turbidity (R = -0.33) and Chl-a (R = -0.35). High spatiotemporal variability was observed in LSWT, turbidity, and Chl-a, along with overall decreasing trends. The findings suggest integrated management strategies to balance water hyacinth eradication and its role in water purification. The results will be vital in decision support systems and preparing strategic plans for sustainable water resource management, environmental protection, and pollution prevention.
城市化、农业和气候变化影响湖泊水质和水葫芦的生长。本研究考察了塔纳湖水面温度、浊度和叶绿素-a（Chl-a）的时空变化及其与水葫芦生物量的关系。使用了 MODIS 陆地/湖泊水面温度（LSWT）、哨兵 2 多光谱成像仪和现场水质数据。验证结果显示，MODIS LSWT 与现场测量的水温（R=0.90）、现场浊度和归一化差异浊度指数（NDTI）（R=0.92）以及现场 Chl-a 和归一化差异叶绿素指数（NDCI）（R=0.84）之间存在很强的正相关关系。LSWT 趋势在整个湖泊中有所不同，东北部、西北部和西南部呈上升趋势，而西部、南部和中部呈下降趋势（2001-2022 年）。在 2001-2022 年期间，降雨前（0.01℃/年）、降雨期（0.02℃/年）和降雨后（0.01℃/年）季节的 LSWT 趋势显著下降，但旱季（0.00℃/年）的 LSWT 趋势非显著增加（P<0.05）。在所有季节中，除了降雨前季节外，平均浊度均呈显著下降趋势（2016-2022 年）。同样，在降雨前和降雨季节，平均 Chl-a 呈显著下降趋势，而在旱季和降雨后季节呈非显著增加趋势（2016-2022 年）。水葫芦生物量与 LSWT 呈正相关（R=0.18），与浊度（R=-0.33）和 Chl-a（R=-0.35）呈负相关。在 LSWT、浊度和 Chl-a 方面观察到高度的时空变异性，同时呈总体下降趋势。研究结果表明，需要采取综合管理策略来平衡水葫芦的根除及其在水净化中的作用。研究结果将对决策支持系统和制定可持续水资源管理、环境保护和污染预防的战略计划至关重要。
