Greenhouse Gas Emissions from Natural and Artificial Lakes in Western Macedonia, Greece

Formation of artificial lakes is a common practice for hydroelectric power generation. Hydroelectricity is considered to be a green and renewable energy source in terms of factory operation. However, hydroelectricity generation may have environmental impact arisen from greenhouse gas (GHG) emissions induced by biomass degradation within water reservoir. Depending on area (rocks, cultivation fields, etc) flooded, an artificial lake may emit significant amounts of GHG, especially in the first years of its formation. In this study, the GHGs emission and water quality of two artificial lakes (Polyfytos and Ilarionas formatted in 1974 and 2012 respectively) and of one natural lake (Zazari) in the area of Western Macedonia were measured and evaluated. Results show that the old Polyfytos lake is stabilized and emits low amounts of CO2 (maximum flux 568 mg/m2/day) and zero CH4.The fresh Ilarionas lake and the natural lake emit higher amounts of CH4 (maximum fluxes 19 and 2200 mg/m2/day respectively). The CO2 emissions depend strongly on time of year and chlorophyll concentration in water (indicator of photosynthetic activity) and even negative fluxes were found in Ilarionas and Zazari (-395 and -732 mg/m2/day respectively). A simple model is used to correlate and predict future GHG emissions by the lakes.