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Have you read article? > Warm climate reservoirs generate methane, a greenhouse gas when the reservoirs are stratified, in which the bottom layers are anoxic (

Have you read article? > Warm climate reservoirs generate methane, a greenhouse gas when the reservoirs are stratified, in which the bottom layers are anoxic (i.e. they lack oxygen), leading to degradation of biomass through anaerobic processes. In warm climate it is methane generator, biomass constantly added with river flow.

Retric 6y ago
Yes, but I don’t think you understand what’s being described. Dam methane production is based on the amount of organic matter being added by the river which is effectively a constant over time. It’s effectively the same process as cow’s methane where decaying plants release methane in a low oxygen environment. The issue is you don’t get an accurate number for the amount of methane in the atmosphere from a dam by multiplying average annual methane release by the number of years it’s in operation. Thus the the rate of doesn’t correlate to future global warming making such statements absolutely meaningless. PS: Also, all of this is assuming the study adjusted for what happens when the dam is not there and nearly the same process occurs when the river dumps into an ocean somewhere.
- sergeykish 6y ago
  Plant either eaten or decays, closed system. Methane does not return upstream only, river flows into ocean, open system. My argument supported by published article and nice picture, look at sediments [1]. Your argument "calculated yearly is not yearly", maybe you should bring some citations, maybe it is you who do not understand what is described. [1] https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxide#Blue_carbon_capture_in_ocean https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxid...
  - Retric 6y ago
    “First, very shallow coastal waters contribute around 50 percent of the total methane emissions from the ocean, despite making up only 5 percent of the ocean area. That's because methane can seep out of natural gas reservoirs along continental margins and can be produced biologically in anoxic (oxygen-depleted) sediments at the seafloor.” https://phys.org/news/2019-10-global-ocean-methane-emissions-dominated.html https://phys.org/news/2019-10-global-ocean-methane-emissions... Dams are collecting the exact same sediments that would end up in estuaries and as that article points out some of that is then turned into Methane. Natural methane is just part of the carbon cycle. It’s generally ignored in oversimplified explanations like you just linked.
    - sergeykish 6y ago
      Thank you. Next sentence > In deep waters, methane is likely to be oxidized as it travels its long route from the seafloor to the atmosphere. Coastal waters emissions does not imply all biomass. Open system — what escapes to deep waters stays there. Quote above implies dam water is warmer.
      - Retric 6y ago
        The very next sentence is “But in shallow waters, there's a rapid route to the atmosphere and methane escapes before it is oxidized.” Most sediment collected by dams ends up there because it weighs more than water and so filters out as soon as the water stops flowing. As rivers reach the ocean that process generally produces vast and very shallow silt deposits. https://en.wikipedia.org/wiki/Estuary https://en.wikipedia.org/wiki/Estuary You can even read about what happens in dam removal when that same sediment flows down stream and ends up very near the surface. There are some very striking images of this processes when muddy flood water reaches the ocean. PS: Also by deep water their talking miles deep. Dead fish end up falling miles in most of the ocean.
        sergeykish 6y ago
        I do not think researches do not understand sediments would deposit somewhere. That's obvious. There should be something else. Turbine gets water not from the surface. There was a project to extract enough methane to increase energy production. http://news.bbc.co.uk/2/hi/6638705.stm http://news.bbc.co.uk/2/hi/6638705.stm
- soperj 6y ago
  Except it doesn't happen in the ocean. There isn't flooded forests in the ocean. Trees take a long time to decay, can be a hundred years in an aerobic environment, but 2-3 times longer in an anaerobic environment.
  - Retric 6y ago
    Most organic matter decaying behind dams is carried in by the river after the initial flooding. Rivers carry a lot of organic matter like tree branches and in floods even entire trees down stream and sometimes all the way to the ocean. Some of that ends up as driftwood on beaches, and some of that gets turned into methane “biologically in anoxic (oxygen-depleted) sediments at the seafloor.” https://phys.org/news/2019-10-global-ocean-methane-emissions-dominated.html https://phys.org/news/2019-10-global-ocean-methane-emissions...
    - soperj 6y ago
      >Most organic matter decaying behind dams is carried in by the river after the initial flooding. What is this based on? The dams producing the most methane have actually flooded forests without removing the trees.
      - Retric 6y ago
        That’s something I heard from someone restocking fish. So, it might be an artifact of US dams being over 50 years old on average, but I assume that generally holds true globally. As to peak methane production, yea that seems reasonable. Though a great many dams didn’t cover forests, so the extremes aren’t representative of the average.
        soperj 6y ago
        Most trees underwater will not have decomposed in 50 years and would still be producing methane.
        6y ago

Retric 6y ago

Yes, but I don’t think you understand what’s being described. Dam methane production is based on the amount of organic matter being added by the river which is effectively a constant over time. It’s effectively the same process as cow’s methane where decaying plants release methane in a low oxygen environment. The issue is you don’t get an accurate number for the amount of methane in the atmosphere from a dam by multiplying average annual methane release by the number of years it’s in operation. Thus the the rate of doesn’t correlate to future global warming making such statements absolutely meaningless. PS: Also, all of this is assuming the study adjusted for what happens when the dam is not there and nearly the same process occurs when the river dumps into an ocean somewhere.

sergeykish 6y ago
Plant either eaten or decays, closed system. Methane does not return upstream only, river flows into ocean, open system. My argument supported by published article and nice picture, look at sediments [1]. Your argument "calculated yearly is not yearly", maybe you should bring some citations, maybe it is you who do not understand what is described. [1] https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxide#Blue_carbon_capture_in_ocean https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxid...
- Retric 6y ago
  “First, very shallow coastal waters contribute around 50 percent of the total methane emissions from the ocean, despite making up only 5 percent of the ocean area. That's because methane can seep out of natural gas reservoirs along continental margins and can be produced biologically in anoxic (oxygen-depleted) sediments at the seafloor.” https://phys.org/news/2019-10-global-ocean-methane-emissions-dominated.html https://phys.org/news/2019-10-global-ocean-methane-emissions... Dams are collecting the exact same sediments that would end up in estuaries and as that article points out some of that is then turned into Methane. Natural methane is just part of the carbon cycle. It’s generally ignored in oversimplified explanations like you just linked.
  - sergeykish 6y ago
    Thank you. Next sentence > In deep waters, methane is likely to be oxidized as it travels its long route from the seafloor to the atmosphere. Coastal waters emissions does not imply all biomass. Open system — what escapes to deep waters stays there. Quote above implies dam water is warmer.
    - Retric 6y ago
      The very next sentence is “But in shallow waters, there's a rapid route to the atmosphere and methane escapes before it is oxidized.” Most sediment collected by dams ends up there because it weighs more than water and so filters out as soon as the water stops flowing. As rivers reach the ocean that process generally produces vast and very shallow silt deposits. https://en.wikipedia.org/wiki/Estuary https://en.wikipedia.org/wiki/Estuary You can even read about what happens in dam removal when that same sediment flows down stream and ends up very near the surface. There are some very striking images of this processes when muddy flood water reaches the ocean. PS: Also by deep water their talking miles deep. Dead fish end up falling miles in most of the ocean.
      - sergeykish 6y ago
        I do not think researches do not understand sediments would deposit somewhere. That's obvious. There should be something else. Turbine gets water not from the surface. There was a project to extract enough methane to increase energy production. http://news.bbc.co.uk/2/hi/6638705.stm http://news.bbc.co.uk/2/hi/6638705.stm
soperj 6y ago
Except it doesn't happen in the ocean. There isn't flooded forests in the ocean. Trees take a long time to decay, can be a hundred years in an aerobic environment, but 2-3 times longer in an anaerobic environment.
- Retric 6y ago
  Most organic matter decaying behind dams is carried in by the river after the initial flooding. Rivers carry a lot of organic matter like tree branches and in floods even entire trees down stream and sometimes all the way to the ocean. Some of that ends up as driftwood on beaches, and some of that gets turned into methane “biologically in anoxic (oxygen-depleted) sediments at the seafloor.” https://phys.org/news/2019-10-global-ocean-methane-emissions-dominated.html https://phys.org/news/2019-10-global-ocean-methane-emissions...
  - soperj 6y ago
    >Most organic matter decaying behind dams is carried in by the river after the initial flooding. What is this based on? The dams producing the most methane have actually flooded forests without removing the trees.
    - Retric 6y ago
      That’s something I heard from someone restocking fish. So, it might be an artifact of US dams being over 50 years old on average, but I assume that generally holds true globally. As to peak methane production, yea that seems reasonable. Though a great many dams didn’t cover forests, so the extremes aren’t representative of the average.
      - soperj 6y ago
        Most trees underwater will not have decomposed in 50 years and would still be producing methane.
        6y ago