Determinants of manual control of water hyacinth expansion over the Lake Tana, Ethiopia

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.

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Water hyacinth: review of its impacts on hydrology and ecosystem services—Lessons for management of Lake Tana

Extreme Hydrology and Climate Variability ◽

10.1016/b978-0-12-815998-9.00019-1 ◽

2019 ◽

pp. 237-251 ◽

Cited By ~ 1

Author(s):

Minychl G. Dersseh ◽

Assefa M. Melesse ◽

Seifu A. Tilahun ◽

Mengiste Abate ◽

Dessalegn C. Dagnew

Keyword(s):

Ecosystem Services ◽

Water Hyacinth ◽

Lake Tana

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Water HyacinthEichhornia crassipes(Mart.) Solms-Laubach Dynamics and Succession in the Nyanza Gulf of Lake Victoria (East Africa): Implications for Water Quality and Biodiversity Conservation

The Scientific World JOURNAL ◽

10.1100/2012/106429 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 13

Author(s):

John Gichuki ◽

Reuben Omondi ◽

Priscillar Boera ◽

Tom Okorut ◽

Ally Said Matano ◽

...

Keyword(s):

Watershed Management ◽

Water Hyacinth ◽

Aquatic Macrophyte ◽

Lake Victoria ◽

Manual Control ◽

Nutrient Loads ◽

Emergent Macrophytes ◽

Aquatic Biodiversity ◽

Multifaceted Approach ◽

Late Stages

This study, conducted in Nyanza Gulf of Lake Victoria, assessed ecological succession and dynamic status of water hyacinth. Results show that water hyacinth is the genesis of macrophyte succession. On establishment, water hyacinth mats are first invaded by native emergent macrophytes,Ipomoea aquaticaForsk., andEnydra fluctuansLour., during early stages of succession. This is followed by hippo grassVossia cuspidata(Roxb.) Griff. in mid- and late stages whose population peaks during climax stages of succession with concomitant decrease in water hyacinth biomass. Hippo grass depends on water hyacinth for buoyancy, anchorage, and nutrients. The study concludes that macrophyte succession alters aquatic biodiversity and that, since water hyacinth infestation and attendant succession are a symptom of broader watershed management and pollution problems, aquatic macrophyte control should include reduction of nutrient loads and implementing multifaceted approach that incorporates biological agents, mechanical/manual control with utilization of harvested weed for cottage industry by local communities.

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Spatiotemporal Dynamics and Environmental Controlling Factors of the Lake Tana Water Hyacinth in Ethiopia

Remote Sensing ◽

10.3390/rs12172706 ◽

2020 ◽

Vol 12 (17) ◽

pp. 2706

Author(s):

Abeyou W. Worqlul ◽

Essayas K. Ayana ◽

Yihun T. Dile ◽

Mamaru A. Moges ◽

Minychl G. Dersseh ◽

...

Keyword(s):

Water Level ◽

Air Temperature ◽

Best Management Practices ◽

Water Hyacinth ◽

Lake Level ◽

Management Practices ◽

Satellite Image ◽

Spatiotemporal Dynamics ◽

Lake Tana ◽

Spatial Coverage

The largest freshwater lake in Ethiopia, Lake Tana, has faced ecological disaster due to water hyacinth (Eichhornia crassipes) infestation. The water hyacinth is a threat not only to the ecology but also to the socioeconomic development of the region and cultural value of the lake, which is registered as a UNESCO reserve. This study aims to map the spatiotemporal dynamics of the water hyacinth using high-resolution PlanetScope satellite images and assesses the major environmental variables that relate to the weed spatial coverage dynamics for the period August 2017 to July 2018. The plausible environmental factors studied affecting the weed dynamics include lake level, water and air temperature, and turbidity. Water temperature and turbidity were estimated from the moderate resolution imaging spectroradiometer (MODIS) satellite image and the water level was estimated using Jason-1 altimetry data while the air temperature was obtained from the nearby meteorological station at Bahir Dar station. The results indicated that water hyacinth coverage was increasing at a rate of 14 ha/day from August to November of 2017. On the other hand, the coverage reduced at a rate of 6 ha/day from December 2017 to June 2018. However, the length of shoreline infestation increased significantly from 4.3 km in August 2017 to 23.4 km in April 2018. Lake level and night-time water temperatures were strongly correlated with water hyacinth spatial coverage (p < 0.05). A drop in the lake water level resulted in a considerable reduction of the infested area, which is also related to decreasing nutrient levels in the water. The water hyacinth expansion dynamics could be altered by treating the nutrient-rich runoff with best management practices along the wetland and in the lake watershed landscape.

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