Abstract
Water hyacinth is a well-known invasive weed in lakes across the world and harms the aquatic environment. Since 2011, the weed has invaded Lake Tana substantially posing a challenge to the ecosystem services of the lake. The major factors which affect the growth of the weed are phosphorus, nitrogen, temperature, pH, salinity, and lake depth. Understanding and investigating the hotspot areas is vital to predict the areas for proper planning of interventions. The main objective of this study is therefore to predict the hotspot areas of the water hyacinth over the surface of the lake using the geographical information system (GIS)-based multi-criteria evaluation (MCE) technique. The main parameters used in the multi-criteria analysis were total phosphorus (>0.08 mg L−1), total nitrogen (>1.1 mg L−1), temperature (<26.2 °C), pH (<8.6), salinity (<0.011%), and depth (<6 m). These parameters were collected from 143 sampling sites on the lake in August, December (2016), and March (2017). Fuzzy overlay spatial analysis was used to overlay the different parameters to obtain the final prediction map of water hyacinth infestation areas. The results indicated that 24,969 ha (8.1%), 21,568.7 ha (7.1%), and 24,036 ha (7.9%) of the lake are susceptible to invasion by the water hyacinth in August, December, and March, respectively. At the maximum historical lake level, 30,728.4 ha will be the potential susceptible area for water hyacinth growth and expansion at the end of the rainy season in August. According to the result of this study, the north and northeastern parts of the lake are highly susceptible for invasion. Hence, water hyacinth management and control plans shall mainly focus on the north and northeastern part of Lake Tana and upstream contributing watersheds.
Highlights
The invasive free-floating aquatic plants have been the main challenges of water bodies in the world because they form a thick floating mat on the water surface that tends to reduce sunlight penetrationWater 2019, 11, 1921; doi:10.3390/w11091921 www.mdpi.com/journal/waterWater 2019, 11, 1921 and the exchange of gases between the water surface and the atmosphere [1,2,3,4,5]
Six water quality parameters were considered in the multi-criteria analysis for the
Six water quality parameters were considered in the multi-criteria analysis for the prediction of hotspot locations and areas in the rainy (August) and dry seasons
Summary
The invasive free-floating aquatic plants have been the main challenges of water bodies in the world because they form a thick floating mat on the water surface that tends to reduce sunlight penetrationWater 2019, 11, 1921; doi:10.3390/w11091921 www.mdpi.com/journal/waterWater 2019, 11, 1921 and the exchange of gases between the water surface and the atmosphere [1,2,3,4,5]. The invasive free-floating aquatic plants have been the main challenges of water bodies in the world because they form a thick floating mat on the water surface that tends to reduce sunlight penetration. Water hyacinth (Eichhornia crassipes [Mart.] Solms), is a perennial, herbaceous, free floating aquatic plant originating in the Amazon Basin, South America [6]. It can grow in stagnant and flowing water bodies [7]. As stated by [11], remarkable freshwater bodies, swamps, and wetland areas of Africa and the Middle East have been invaded by this invasive weed. Factors that can create favorable conditions for this growth can be salinity, pH, temperature, sunlight shading, disturbance, and reproduction systems of the invasive weed [12]
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