Investigating current and potential expansion, socioeconomic impact and climate smart management of Water Hyacinth (Eichhornia Crassipes) in the Rift Valley lakes of Ethiopia

This thesis presents a study on water hyacinths' (WH) (Eichhornia Crassipes) current and potential expansion, socioeconomic impact, and climate-smart management approach in two selected lakes in Ethiopia. The study main goal was to assess an integrated and effective climate-smart management approach that reduces the impact of WH in the Rift Valley of Ethiopia. Field observation and survey were conducted to evaluate the WH's current distribution, potential expansion, and impact. Further data were collected through a household survey, Key Informant Interview, Focus Group Discussion, Landsat images, and field and laboratory water sample tests to characterize the lake water physicochemical nature at WH-infected sites and non-infected sites. During WH's socioeconomic and environmental impact assessment, a total of 413 households were sampled, and the data were analyzed using descriptive statistics, t-test, and Multivariate test. Water samples from four different locations selected on each lake, were analyzed for the selected physicochemical properties such as phosphate, nitrate-nitrogen, Acidity or Basicity(pH), Biological oxygen demand (BOD5), temperature (T in 0C), and selected heavy metals such as Chromium (Cr), Lead (Pb), Cadmium (Cd), Zinc (Zn), and Copper (Cu). The collected data subjected to statistical analysis was compared using the ANOVA test to assess the impact of water hyacinth causing deviation from the normal level of lake water physicochemical character. According to land use and land cover data, the water hyacinth's rate of spread was 0.56% in Lake Koka and 0.95% in Lake Ziway. The study showed that the spread of water hyacinth increased drastically between 2013 and 2025 at both Lake Koka and Lake Ziway. Despite the chemical oxygen demand (COD) of Lake Ziway, this study found no significant (p > 0.05) variation in the concentrations of Cu, EC, pH, and water temperature between wet and dry seasons in either lake. Variations in Zn concentration and other physicochemical parameters (EC, BOD5, COD, nitrate, phosphate) between low, medium, and high levels of water hyacinth were significant in both lakes (p<0.05). Water hyacinth has shown significant phytoremediation nature during wet and dry seasons. The lowest average heavy metal, phosphate, and nitrate concentrations and significant pH and temperature variations were observed in Lakes Koka and Lake Ziway, among water hyacinth and other grass-infested sites. In the Lake Koka district, WH caused food insecurity to 51% of the participants by reducing food productivity and health distress to 98.5% through exposure to vector disease. In Lake Ziway district, it exposed 81.6% of the participants to food insecurity and 99.5% to health distress. In both lakes, WH affected the fishing industry according to 99.8% of the participants. In terms of crop production, at Koka, maize production was significantly affected, ᵡ2 (1, = 413) = 117.01, p<.001, while at Ziway cabbage production was significantly affected, ᵡ2 (1, N= 413) =6.36, p<.001. There was a significant difference in annual income level, household leader's age, and recovery cost according to household family size, F (9, 623.18) =14.38, p<.001; Wilk's Λ=.632, partial η2=.14. Regarding Climate-Smart management, the household survey showed that the wetlands owned by 92.0% of the participants were affected by WH invasion. Additionally, 69.3% of the participants confirmed that the water quality of the lake water had been deteriorated and 74.1% of deforestation and loss of native grasses due to WH invasion in the districts. The results of this study revealed the signals of land use and land cover change due to water hyacinth invasion in the Upper Awash Basin, which is considered an important aspect of future water resources planning and management. Additionally, WH and environmental chemical interaction suggest that the water hyacinth plant is a promising nature-based solution for removing undesirable chemicals from contaminated water bodies. Further, the early detection and control of WH spread in the locality needs to be based on citizen science so that the community members can act in time to control the spread of WH by themselves. The study recommends that wetland restoration, water quality reestablishment, afforestation, and rehabilitation of native vegetation be done as part of climate-smart management for WH control and better management. Therefore, effective management and control of WH requires coordination of controlling effort, proper participation of the local people, and involvement of different experts. In addition, this study recommends exploring the benefits of plants to nature and humans, including biomass production and ecosystem services

Environmental Sciences

D. Phil (Environmental Science)