Reservoirs are designed for water supply, irrigation, flood control, navigation, hydropower, recreation, tourism, etc. and sometimes also used for more than one purpose. Studies show that reservoirs can change the GHG balance, acting as both sinks or sources sometimes even within the same reservoir. The introduction of a reservoir may change the pattern of emissions in the watershed. Most reservoirs including natural lakes are able to store carbon, originating from organic or inorganic material, in the reservoir’s sediments. Many different factors influence the possibility of reservoirs to emit GHGs. Age, shape, water depth, water temperature, climate and weather conditions, plant life in the water, soil types in the watershed; longevity of water stays in the reservoir are the main parameters/factors affecting GHG production. To properly calculate the carbon footprint of freshwater reservoirs it is necessary to evaluate the carbon footprint, taking into consideration the whole Carbon Cycle, and estimating the net GHG emissions from the reservoir. To establish the net impact of a reservoir, emissions resulting from natural and unrelated human activity must first be deducted. The difference between the emissions with and without the reservoir should be calculated. The result is referred to as the reservoir’s net GHG emissions, or GHG footprint.

Dear sir/ friends

GHG emissions from reservoirs and lakes is major problem now a days. Its mainly due to the degradation of organic carbon in the reservoirs/ Lakes. Out of the all organic carbon, Labile organic carbon is mainly responsible for GHG emissions. Reservoirs behaves like a source or sink is mainly depends on the Depth, Temperature, Organic matter input, C:N ratio etc. So net emissions should be calculate near by area or in the same eco-region before constructing any reservoirs. GHG emissions can be reduce from the reservoirs and lake by dredging periodically, capture methane emissions and its use for the Energy generation, which will reduce the climate change effect as well as full fill the demand of energy.

Dams/reservoirs emit GHGs in a number of ways such as, from breakdown/decomposition of soil and plant carbon, anaerobic conversion of organic carbon to CH4 and rotting/decay of vegetation at the bottom of dams/lakes. GHG gases are released into the atmosphere from dams/reservoirs via direct diffusion from the surface, or bubbling or diffusion via turbine. Temperature, age of dams/reservoirs, amount of vegetation and depth of dams/reservoirs can influence the amount of GHG emissions from reservoirs. For example, reservoirs in tropical environments have been found to have significantly increased emissions than reservoirs in boreal and temperate climates

Hi,

We have done research in this area for many years, we found the GHG emission level should be different in different climate zone. According to the research we did in Three Gorges Reservoir (one of the biggest reservoirs in the world), we found that the GHG emission level will increase when compared with the level before, however it will decrease as time goes by. You can find our publication at DOI: 10.1038/srep04449.

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