Feyera SenbetaAssefa SeyoumEngdawork AssefaAssefa Gudina2026-05-252026-05-252025https://etd.aau.edu.et/handle/123456789/8120Water hyacinth, an invasive aquatic weed, poses significant challenges to aquatic ecosystems globally. Since the early 1950s, the plants have been expanding aggressively and affecting the natural ecosystems and livelihoods of the community in the Central Rift Valley of Ethiopia. The infestation of weeds has been substantially exacerbated by the excessive nutrient loading from the surrounding farmlands into the lake system, particularly nitrogen and phosphorus. This study explores the trends of water hyacinth infestations in Koka and Dembel lakes in the Central Rift Valley of Ethiopia. The study explored the interface between land use/land cover changes (LULCC) and the proliferation of water hyacinth, its impacts on the environment and livelihood, and management frameworks. Data was gathered from 348 households, six focus group discussions, and interviews with 6 key informants from diverse groups. Propensity Scores, Difference-in-Differences, and Weighted Least Squares methods were applied to evaluate the effects of the plants on livelihoods and ecosystem services. Field observations and satellite imagery were also utilized to assess LULCC and water hyacinth spread. To evaluate the impact of the plant on water quality, twenty-four water samples were collected using pre-cleaned polyethylene bottles. Following the standard procedures of water lab analysis, water parameters such as PH, Dissolved Oxygen (DO), Temperature, Total Nitrogen (TN) and Nitrate-Nitrogen (NO3-N), Ammonia-Nitrogen (NH3-N), Total Phosphorus (TP) and Soluble Reactive Phosphate (SRP-PO4), Sulphate and Sulfide and salinity were also analyzed. The study revealed that water hyacinth's adverse effects outweigh its benefits. In Lake Dembel, coverage increased from zero in 1994 to over 4,000 hectares by 2024, with a similar expansion in Koka Lake. LULCC due to agricultural expansion, urbanization, and deforestation contributed to increased nutrient runoff, promoting water hyacinth growth. This led to increased sedimentation and nutrient runoff into the lakes of Koka and Dembel which in turn promoted the growth and expansion of water hyacinth. The feedback loop between LULCC changes and water hyacinth proliferation is a complex, self-reinforcing cycle. Historical data underscore a significant rise in total phosphorus concentrations, particularly in Lake Koka, attributed to effluent discharge and agricultural runoff. Lake Dembel showed TN (0.47–7.86 mg/L) and TP (0.07–1.64 mg/L), with TP exceeding eutrophication thresholds. Lake Koka had higher pollution, with TN (0.83–8.96 mg/L) and TP (0.14–3.8 mg/L), particularly near agricultural inflows. The assessments indicate alarmingly high nutrient levels, with Lake Koka exhibiting higher pollution loads than Lake Dembel. The nutrient concentrations surpass eutrophication thresholds in both lakes, necessitating urgent management. The expansion of the plant is currently disrupting the hydrological system, affecting fishing and navigation, and leading to socio-economic losses for the local community. The result of Difference-in-Differences shows a decline in the total annual income by 823 ETB, income from crop production by 329 ETB per year, and income from off-farm activities by 6952 ETB per year for those living adjacent to the invaded lakes. Although the impact varies according to the intensity of the water hyacinth infestation, it adversely affects rural livelihoods by reducing crop yields and returns from off-farm activities. The study results showed that 96 percent of the respondents are willing to participate in management practices through labor contribution. However, the willingness to contribute labor is affected by the initial and secondary bids, gender, lakes’ water quality knowledge, livestock size, and educational status. Despite the existence of various comprehensive policies related to water hyacinth management, the study revealed that the practical implementation of these regulations is far from ideal, owing primarily to resource constraints, insufficient integration of policy measures, and a lack of robust enforcement mechanisms. Effective management requires integrated strategies addressing both land use practices and invasive species control. The study emphasizes the need for coordinated management efforts to restore the impacts of water hyacinth on the ecological and socio-economic value of Lakes Koka and Dembel. The study recommended effective management of water hyacinth in Lakes Koka and Dembel requires integrated strategies that address both land use practices and invasive species control, with a strong emphasis on policy enforcement, community involvement, and resource allocation to mitigate the ecological and socio-economic impacts of this invasive weed. Keywords: Water Hyacinth, Environment, Ecology, Livelihood, Institutions, stakeholder, Rift Valley, Koka, Dembel.enWater HyacinthEnvironmentEcologyLivelihoodInstitutionsstakeholderRift ValleyKokaDembel.Dissertation