Abstract
Water hyacinth originated from the Amazon Basin and has expanded to other parts of the world since the 1800s. In Ethiopia, the weed is affecting the socio-economic activities of the people whose livelihood is directly or indirectly dependent on Lake Tana. Still, the area covered by water hyacinth and the impact of water level fluctuation on the expansion of water hyacinth has not been known clearly. Therefore, the main objective of this study was to determine the spatiotemporal distribution of water hyacinth and relation with lake-level fluctuation. The area covered by water hyacinth was determined using monthly Sentinel-2 images, which were collected from November 2015 to December 2019. The impact of water level fluctuation on the expansion of water hyacinth was evaluated using hourly water level data converted to a monthly average to correlate with the area covered by the water hyacinth. In addition, MOD13Q1.006 data was used to evaluate the trend of the Normalized Difference Vegetation Index (NDVI) and its linkage with the weed. The maximum areas covered by water hyacinth were 278.3, 613.6, 1108.7, 2036.5, and 2504.5 ha in Feb 2015, October 2016, September 2017, December 2018, and in December 2019, respectively. Its areal coverage was declining from the northern corridors and increasing in eastern shores of the lake. The lake-level fluctuation was observed in the range of 1.5 to 3.98 m in this study. The annual mean maximum spatial values of the NDVI were in the range of 0.27 and 0.47. The area covered by water hyacinth was increasing significantly (P < 0.05) and positively correlated with the seasonal lake-level fluctuation. High water level enabled the expansion of the weed by extending its suitable habitat of shallow water to the flood plain. Based on the results of this study, lake-level fluctuations can have an adverse impact on the expansion of the weed.
Highlights
IntroductionThe species of this invasive weed was discovered by a German Naturalist, C
Water hyacinth (Eichhornia crassipes [Mart.] Solms) originated from the Amazon Basin, SouthAmerica
The specific objectives of this study were to (1) map and analyze the spatiotemporal dynamics of water hyacinth in Lake Tana (2015–2019), (2) examine the linkage between the invaded areas of the lake and the lake hydrology, and (3) investigate the temporal linkage of Normalized Difference Vegetation Indices (NDVI) and the area covered by water hyacinth
Summary
The species of this invasive weed was discovered by a German Naturalist, C. Water 2020, 12, 1435 since the 1800s [1,2,3] It is one of the world’s worst invasive weeds, categorized as one of the hundred most harmful invasive species, and one of the top ten worst weed in the globe [2,4,5,6,7]. The expansion rate of water hyacinth is very quick and its eradication is very difficult since it can double its biomass every 5 days. Due to its increasing mesophyll conductance, soluble protein content per unit area, and specific leaf weight, water hyacinth has a maximum photosynthetic capacity [11]
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