Title: Influence of Land Use and Land Cover on Riverine Greenhouse Gas Emissions in an Afro-montane Catchment, Ethiopia
Author: Belvine Jepchumba Rotich
Supervising Institution: IHE Delft Institute for Water Education
Year: 2024
Abstract:
Riverine systems play an important role in catchment-scale greenhouse gas emissions through in situ biogeochemical cycling of carbon and nitrogen. River systems are significant in the water cycle and in supporting livelihoods of people who rely on their services. Anthropogenic activities have resulted in increased riverine GHG emission which has been understudied in African montane rivers. This has led to large uncertainties in the estimates caused by limited data. To fill this gap, I conducted a study in the Wondo Genet catchment in Southern Ethiopia from January to March 2024 to assess the effects of land use and land cover on GHG concentrations. The potential contribution of springs to GHG emission was also assessed. I sampled 51stream sites and three spring sites in two sub catchments, Werka and Wesha rivers during the dry -to-rainy season January to March 2024. Agricultural stream sites in the uplands and lowlands and in agriculture and settlement sites had the highest concentration of CH4, CO2 and N2O compared to stream sites in the forest. Concentration of CH4 in the upland sites was 10.85 ± 1.59 (μg/l), while CO2 and N2O concentrations were 0.27 ± 0.04 (mg/l) and 3.48 ± 1.55 (μg/l) respectively. The concentration in agriculture and settlement sites were 12.32 ± 1.04 (mg/l) for CH4, 0.31 ± 0.03 (mg/l) for CO2 and 2.36 ± 0.51(μg/l) for N2O. In the lowland sites, CH4 concentrations were 3. 84 ± 0.65 (μg/l), CO2 concentration was 0.34 ± 0.05 (mg/l) and N2O was 2.94 ± 0.68 (μg/l). Forest CH4 concentrations were 0.36 ± 0.12 (μg/l) while CO2 concentrations were 0.02 ± 0.00 and 0.07 ± 0.04 for N2O. Predictive water quality variable for CH4 was DO, while CO2 and N2O were positively related to TDN (mg/l) and NO3 – N (mg/l) and negatively with pH and DO (mg/l). Groundwater inflows to streams are potentially an important source of both CO2 and N2O to riverine concentrations. I concluded that nitrification was dominant in forested sites, while denitrification was responsible for N2O release in agricultural sites.
Keywords: River ecology, Green house gases, land cover, land use, human impacts, pollution, Groundwater, carbon and nitrogren cyclying, nitrification, Ethiopia