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Methane emissions from reservoirs: Assessing the magnitude and developing mitigation approaches - Maine
Citation:
Beaulieu, J. Methane emissions from reservoirs: Assessing the magnitude and developing mitigation approaches - Maine. Seminar Series, Waterville,ME, March 23, 2018.
Impact/Purpose:
There are more than 16 million reservoirs worldwide which are equivalent to a combined volume of Lakes Huron and Michigan, or 10% of the water stored in all-natural freshwater lakes on Earth. The creation of large dams is accelerating in developing countries. There are many benefits of reservoirs: navigation, flood control, recreation, and drinking water. Reservoirs & biogeochemical change Retain an order of magnitude more N and S per unit area than lakes (Harrison 2009, 2012). Bury more organic C than world oceans (Tranvik et al. 2009). Impounded waters support higher rates of methane (CH4) production than free flowing rivers. Suspended sediment is deposited. Less oxygen delivery to sediments. Inundated vegetation can be converted to CH4. CH4 in the Atmosphere. Methane (CH4) is the second largest contributor to climate change. Atmospheric levels are higher than anytime in previous 700,000 years. Objectives: Generate a reservoir-scale estimate of CH4 emission, with appropriate confidence intervals, that accounts for the spatial distribution of measured emission rates. Approach Generalized Random Tessellation Stratified (GRTS) Survey Designs Survey design. All areas of reservoir have equal probability of being sampled. Emphasize spatial-balance. Data analysis Probability sample producing design-based estimates of central tendency and variance at the whole-system scale. Conclusions: Intentional drawdown events can trigger a pulse of CH4 release to the atmosphere. Drawdowns can contribute disproportionately to total CH4 ebullition. Drawdown effects are strongest in shallow waters. Drawdown related emissions may be mitigatable. Minimize the frequency of drawdown events. Minimize the drawdown rate. Delay fall drawdowns until after lake circulation in the fall when much of the CH4 pool may be oxidized to CO2.
Description:
There are more than 16 million reservoirs worldwide which are equivalent to a combined volume of Lakes Huron and Michigan, or 10% of the water stored in all-natural freshwater lakes on Earth. The creation of large dams is accelerating in developing countries. There are many benefits of reservoirs: navigation, flood control, recreation, and drinking water. Reservoirs & biogeochemical change Retain an order of magnitude more N and S per unit area than lakes (Harrison 2009, 2012). Bury more organic C than world oceans (Tranvik et al. 2009). Impounded waters support higher rates of methane (CH4) production than free flowing rivers. Suspended sediment is deposited. Less oxygen delivery to sediments. Inundated vegetation can be converted to CH4. CH4 in the Atmosphere. Methane (CH4) is the second largest contributor to climate change. Atmospheric levels are higher than anytime in previous 700,000 years. Objectives: Generate a reservoir-scale estimate of CH4 emission, with appropriate confidence intervals, that accounts for the spatial distribution of measured emission rates. Approach Generalized Random Tessellation Stratified (GRTS) Survey Designs Survey design. All areas of reservoir have equal probability of being sampled. Emphasize spatial-balance. Data analysis Probability sample producing design-based estimates of central tendency and variance at the whole-system scale. Conclusions: Intentional drawdown events can trigger a pulse of CH4 release to the atmosphere. Drawdowns can contribute disproportionately to total CH4 ebullition. Drawdown effects are strongest in shallow waters. Drawdown related emissions may be mitigatable. Minimize the frequency of drawdown events. Minimize the drawdown rate. Delay fall drawdowns until after lake circulation in the fall when much of the CH4 pool may be oxidized to CO2.