4 ms·

Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It's Slowing Down

68 points by pseudolus 1y ago

libpcap 1y ago
Why not use pumps to increase mixing?
- maxbond 1y ago
  It's an interesting question, here's some napkin math. There's almost 19 gigaliters of water in Crater Lake. To pump that amount of water in a year would require pumping 52 megaliters of water per day. A small city produces about 200 megaliters of sewage in a day. (LA produces about 2 gigaliters per day.) So it should be possible but would be very expensive. Maybe on the order of running the drinking water infrastructure for a town. I suspect I'm overestimating though, I think you might only have to pump half of the water to achieve good mixing. (ETA: After a tiny bit of research I think you might be able to do it with much less than half due to entrainment.) You would also kill a lot of animals and microorganisms in the process. Pumps driven by impellers create cavitation that cracks open microorganisms, and things like peristaltic pumps which avoid this can't handle these volumes. As this material is decomposed by bacteria, they will reproduce and increase the biological oxygen demand in the water, which might end up making the lake anoxic anyway.
  - eCa 1y ago
    In addition to that, how many lakes would need to be pumped or would it be a feel-good project for famous lakes?
  - Terr_ 1y ago
    I wonder if there are any elegant passive solutions... like a floating sun-exposed surface that conducts heat down to a lower anchored point. Or lake-bottom structures that re-channel water movements from subtle tides or seiches.
    - vanderZwan 1y ago
      I think that's the wrong way round: climate change causes longer summers and shorter winters, so the problem is one of cooling, not heating. Shade balls[0] could work, but then they'd have to cover part of the lake with that. EDIT: And of course, that also comes with a reduction in total light reaching the lake, which may have different side effects beyond temperature alone. [0] https://www.youtube.com/watch?v=uxPdPpi5W4o https://www.youtube.com/watch?v=uxPdPpi5W4o
      - cnnlives3855 1y ago
        I think what they’re saying is that if you have sufficient heat at the bottom, hotter water rises, so you get cycling.
        vanderZwan 1y ago
        Look at the full picture. The cycling is reduced due a reduction in temperature gradient. That reduction in temperature gradient is due to water not cooling down enough in winter and warming up for longer in summer. Could you increase cycling by creating a temperature gradient by capturing the heat from the sun to warm up the water at the bottom of the lake? Maybe, but that also would imply an even greater increase of average water temperature than the effects of climate change. Which would have all kinds of other ecological side-effects. Or put another way: global warming increases thermal energy being added to the system, resulting in a change of the dynamics of the lake. Cooling it would counteract that increase. Capturing more heat would add even more thermal energy. Even if they both could affect cycling in the same way, adding even more thermal energy is almost guaranteed to create other ecosystemic imbalances.
    - QuadmasterXLII 1y ago
      You could store well sealed nuclear waste in it, and stir by convection. Definitely won’t go wrong, no flaws here.
  - water-your-self 1y ago
    Perhaps a large horizontal whisk. Do fluids appreciate sheer force when it is parallel to gravity?
  - adrianN 1y ago
    I wonder whether it’s better to pump air down instead of pumping water up.
  - Retric 1y ago
    That’s overly simplified, and these lakes normally only fully mix every few years. In winter surface water is colder than sub surface water so if you start pumping water to create a cold and more dense column of water in a pipe you can stop the pump and let physics move the through that pipe for months with zero energy expenditure. It’s the same basic reason lakes normally mix in the first place. Decomposing organic mater etc then warm up the deep water over time Even without that it’s way more efficient to pump water when you have near zero difference in pressure and only need to move a short distance. The column of water outside the pump and the column of water inside the pump are only going to vary by the difference in weight due to differences in temperature. So you’re effectively pumping water up ~10cm even though the column is much longer than that. If we assume we need ultra fast circulation and mixing every year… 19 gigaliter ~= 19 billion kg lifted ~0.1 m is 9.8 * 19 ^9 * 0.1 J / 60 / 24 / 365 = 600 Kw which is a fair bit of energy perhaps 1 MW with losses, definitely expensive for an individual but not much compared to what cities are spending pumping water around. But again you’re likely fine doing less than 1% of that.
- monster_truck 1y ago
  Based on nothing, I suspect a giant spoon would be better
- RGamma 1y ago
  Modern society is falling apart over the cost of getting to net zero. I don't think we have the funds to put lakes on artificial life support in the foreseeable future.
  - theklub 1y ago
    Actually it’s already done in some places. https://www.easthamptonct.gov/sites/g/files/vyhlif7556/f/uploads/three_phased_approach_to_lake_pocotopaug_health.pdf https://www.easthamptonct.gov/sites/g/files/vyhlif7556/f/upl...
  - potato3732842 1y ago
    Is it the cost of net zero? Or is it the cost of everything else pretending to be relevant to net zero? Of the interests pushing for net zero, the bulk of them are only doing it insofar as it can be done in a way that basically guarantees them incomes and all of these earmarks are what's driving the non-starter cost while simultaneously souring people on the whole premise. You'd think that people who allege to think on environmental time scales wouldn't need to be told that a movement that looks like branded rent seeking and legalized corruption when viewed through the perspective of anyone who isn't rolling in money isn't gonna last long enough to do its job.
  - FrustratedMonky 1y ago
    "over the cost of getting to net zero" Really? Where? Sure looks like we've completely given up. Where are these costs? Who is spending any money on Net-Zero.
    - lazide 1y ago
      Germany and their out of control energy costs (while still only being at best 1/5 of the way there if you count things like thermal heat), are a good example. California has a dramatically easier climate, and is similarly struggling - without even taking into account goods shipping/transportation, thermal heat in the less nice climate zones, etc. California might have a chance of getting to actual net zero without completely breaking the bank. But it’s not obvious it will. Germany is an order of magnitude harder.
bearsandsalmon 1y ago
Some more ideas that might work: - Explosives. Drop large explosives deep into the lake periodically. It may kill a lot of life, but if you need to stir up organic matter at the bottom, it’s more efficient than attempting to stir it. - Migrate life from similar depths at other lakes. If it’s going to die if you don’t, maybe it’s worth the effort. - Drill. Just drill a deep hole until you get to a water source or heat.
acyou 1y ago
Algal blooms with limited mixing sounds like a pretty good carbon capture mechanism! I wonder if there is oil and gas at the bottom of any of these deep lakes? /s It would be interesting to know the gas balances for these lakes, in particular how reduced mixing affects methanotrophy and methanogenesis. If its talking about climate change, this article really should discuss methane, I think that's a bigger deal.
- dredmorbius 1y ago
  This is a mechanism by which some oil deposits are thought to have formed, and by which a large quantity of biospheric carbon was sequestered during earlier warm spells, refered to as the Eocene Azolla Event. Essentially: arctic seas formed fresh-water "lenses" through meltwater, which promoted plant growth (in particular azolla, though likely also algae and plankton). This growth then sank to the sea-floor, depositing as oils (and much ultimately undergoing keroginisation to form petroleum). <https://en.wikipedia.org/wiki/Azolla_event https://en.wikipedia.org/wiki/Azolla_event> Similar mechanisms have been proposed for addressing carbon sequestration goals in the present, e.g., "CO2 sequestration by propagation of the fast-growing Azolla spp. " <https://pmc.ncbi.nlm.nih.gov/articles/PMC8520330/ https://pmc.ncbi.nlm.nih.gov/articles/PMC8520330/>.
- maxbond 1y ago
  It could also be the opposite of a carbon capture mechanism is the detritus if those algal blooms are broken down by archaea and turned into methane, which could then return to the atmosphere. Methane is about 30 times more potent a greenhouse gas than CO2.
samirillian 1y ago
Common problem in man-made lakes. When you create a lake by damming a river it creates perfect conditions for lamination, deep narrow and filled with agricultural runoff. When they pull the plug on these dams all the de-oxygenated water flows out the bottom, basically just dumping unbreathable water into the river killing off the more sensitive fish, eg trout die catfish live, and smelling like a million firecrackers.
joek1301 1y ago
I know they aren't the point of the article, but the photos are absolutely breathtaking.
- fellowniusmonk 1y ago
  It's impossible to take a bad picture of crater lake, it's still the single most photogenic anything I've ever seen, there may be equals but nothing superior.
  - nullstyle 1y ago
    If you feel this way, i recommend you go visit alaska; even just hiking hatcher’s pass on a good day outweighs crater lake in beauty for me.
  - chihuahua 1y ago
    I feel like there are lots of places in Central Oregon that are on the same level. Anything near the 3 sisters - McArthur Rim Trail, Highway 242, McKenzie River, Clear Lake, Sparks Lake. And Newberry Crater - it's like Crater Lake, but without the crowds. You can drive up to the top of East Paulina Peak and you're probably the only person up there. The Great Obsidian Flow is nearby. And there's a trail going all the way around the top of the crater. You can spend 2 hours riding a MTB along that trail, and probably meet 0 other people.
ravedave5 1y ago
There weren't even fish in the lake until 1888, it's likely this has occurred more than once in the past.
- ericmcer 1y ago
  I am not sure if they still plant fish at Crater lake. If you have spent much time fishing you will pretty quickly learn that almost every accessible lake in the US is regularly stocked with fish. I would say the "native" freshwater fish population is so decimated at this point that if you want to catch something you either seek out inaccessible places that have seen little human contact, or you follow the fish plantings and catch planted fish. The idea of a lake that thousands of humans regularly access having a healthy ecology seems far fetched.
  - margalabargala 1y ago
    They do not stock the lake anymore, no. The fish currently in it are considered invasive by the park and there are no catch limits. It's odd the article poses this as a "problem" in an article about Crater Lake, where uniquely among lakes this "problem" is most likely to just fix the other problem. Kill all the fish in the lake and the lake is better off.
    - maxbond 1y ago
      It won't selectively kill fish, it'll kill frogs, turtles, algae, and anything else that lives in the water which isn't a bacteria or archaea capable of living in an anoxic environment. Possibly also the predators of those species which live on land.
      - margalabargala 1y ago
        > it'll kill frogs, turtles, algae, and anything else that lives in the water which isn't a bacteria or archaea capable of living in an anoxic environment That's a bit dramatic. Frogs, turtles, salamanders, etc, can breathe air. The only predators are birds, who can find food at any of the many other lakes in the area. Crater Lake's geography is essentially unique among lakes that may be having this issue. There is a near-total lack of native fauna that would be affected by an anoxic event.

68 points by pseudolus 1y ago

libpcap 1y ago

Why not use pumps to increase mixing?

maxbond 1y ago
It's an interesting question, here's some napkin math. There's almost 19 gigaliters of water in Crater Lake. To pump that amount of water in a year would require pumping 52 megaliters of water per day. A small city produces about 200 megaliters of sewage in a day. (LA produces about 2 gigaliters per day.) So it should be possible but would be very expensive. Maybe on the order of running the drinking water infrastructure for a town. I suspect I'm overestimating though, I think you might only have to pump half of the water to achieve good mixing. (ETA: After a tiny bit of research I think you might be able to do it with much less than half due to entrainment.) You would also kill a lot of animals and microorganisms in the process. Pumps driven by impellers create cavitation that cracks open microorganisms, and things like peristaltic pumps which avoid this can't handle these volumes. As this material is decomposed by bacteria, they will reproduce and increase the biological oxygen demand in the water, which might end up making the lake anoxic anyway.
- eCa 1y ago
  In addition to that, how many lakes would need to be pumped or would it be a feel-good project for famous lakes?
- Terr_ 1y ago
  I wonder if there are any elegant passive solutions... like a floating sun-exposed surface that conducts heat down to a lower anchored point. Or lake-bottom structures that re-channel water movements from subtle tides or seiches.
  - vanderZwan 1y ago
    I think that's the wrong way round: climate change causes longer summers and shorter winters, so the problem is one of cooling, not heating. Shade balls[0] could work, but then they'd have to cover part of the lake with that. EDIT: And of course, that also comes with a reduction in total light reaching the lake, which may have different side effects beyond temperature alone. [0] https://www.youtube.com/watch?v=uxPdPpi5W4o https://www.youtube.com/watch?v=uxPdPpi5W4o
    - cnnlives3855 1y ago
      I think what they’re saying is that if you have sufficient heat at the bottom, hotter water rises, so you get cycling.
      - vanderZwan 1y ago
        Look at the full picture. The cycling is reduced due a reduction in temperature gradient. That reduction in temperature gradient is due to water not cooling down enough in winter and warming up for longer in summer. Could you increase cycling by creating a temperature gradient by capturing the heat from the sun to warm up the water at the bottom of the lake? Maybe, but that also would imply an even greater increase of average water temperature than the effects of climate change. Which would have all kinds of other ecological side-effects. Or put another way: global warming increases thermal energy being added to the system, resulting in a change of the dynamics of the lake. Cooling it would counteract that increase. Capturing more heat would add even more thermal energy. Even if they both could affect cycling in the same way, adding even more thermal energy is almost guaranteed to create other ecosystemic imbalances.
  - QuadmasterXLII 1y ago
    You could store well sealed nuclear waste in it, and stir by convection. Definitely won’t go wrong, no flaws here.
- water-your-self 1y ago
  Perhaps a large horizontal whisk. Do fluids appreciate sheer force when it is parallel to gravity?
- adrianN 1y ago
  I wonder whether it’s better to pump air down instead of pumping water up.
- Retric 1y ago
  That’s overly simplified, and these lakes normally only fully mix every few years. In winter surface water is colder than sub surface water so if you start pumping water to create a cold and more dense column of water in a pipe you can stop the pump and let physics move the through that pipe for months with zero energy expenditure. It’s the same basic reason lakes normally mix in the first place. Decomposing organic mater etc then warm up the deep water over time Even without that it’s way more efficient to pump water when you have near zero difference in pressure and only need to move a short distance. The column of water outside the pump and the column of water inside the pump are only going to vary by the difference in weight due to differences in temperature. So you’re effectively pumping water up ~10cm even though the column is much longer than that. If we assume we need ultra fast circulation and mixing every year… 19 gigaliter ~= 19 billion kg lifted ~0.1 m is 9.8 * 19 ^9 * 0.1 J / 60 / 24 / 365 = 600 Kw which is a fair bit of energy perhaps 1 MW with losses, definitely expensive for an individual but not much compared to what cities are spending pumping water around. But again you’re likely fine doing less than 1% of that.
monster_truck 1y ago
Based on nothing, I suspect a giant spoon would be better
RGamma 1y ago
Modern society is falling apart over the cost of getting to net zero. I don't think we have the funds to put lakes on artificial life support in the foreseeable future.
- theklub 1y ago
  Actually it’s already done in some places. https://www.easthamptonct.gov/sites/g/files/vyhlif7556/f/uploads/three_phased_approach_to_lake_pocotopaug_health.pdf https://www.easthamptonct.gov/sites/g/files/vyhlif7556/f/upl...
- potato3732842 1y ago
  Is it the cost of net zero? Or is it the cost of everything else pretending to be relevant to net zero? Of the interests pushing for net zero, the bulk of them are only doing it insofar as it can be done in a way that basically guarantees them incomes and all of these earmarks are what's driving the non-starter cost while simultaneously souring people on the whole premise. You'd think that people who allege to think on environmental time scales wouldn't need to be told that a movement that looks like branded rent seeking and legalized corruption when viewed through the perspective of anyone who isn't rolling in money isn't gonna last long enough to do its job.
- FrustratedMonky 1y ago
  "over the cost of getting to net zero" Really? Where? Sure looks like we've completely given up. Where are these costs? Who is spending any money on Net-Zero.
  - lazide 1y ago
    Germany and their out of control energy costs (while still only being at best 1/5 of the way there if you count things like thermal heat), are a good example. California has a dramatically easier climate, and is similarly struggling - without even taking into account goods shipping/transportation, thermal heat in the less nice climate zones, etc. California might have a chance of getting to actual net zero without completely breaking the bank. But it’s not obvious it will. Germany is an order of magnitude harder.

bearsandsalmon 1y ago

Some more ideas that might work: - Explosives. Drop large explosives deep into the lake periodically. It may kill a lot of life, but if you need to stir up organic matter at the bottom, it’s more efficient than attempting to stir it. - Migrate life from similar depths at other lakes. If it’s going to die if you don’t, maybe it’s worth the effort. - Drill. Just drill a deep hole until you get to a water source or heat.

acyou 1y ago

Algal blooms with limited mixing sounds like a pretty good carbon capture mechanism! I wonder if there is oil and gas at the bottom of any of these deep lakes? /s It would be interesting to know the gas balances for these lakes, in particular how reduced mixing affects methanotrophy and methanogenesis. If its talking about climate change, this article really should discuss methane, I think that's a bigger deal.

dredmorbius 1y ago
This is a mechanism by which some oil deposits are thought to have formed, and by which a large quantity of biospheric carbon was sequestered during earlier warm spells, refered to as the Eocene Azolla Event. Essentially: arctic seas formed fresh-water "lenses" through meltwater, which promoted plant growth (in particular azolla, though likely also algae and plankton). This growth then sank to the sea-floor, depositing as oils (and much ultimately undergoing keroginisation to form petroleum). <https://en.wikipedia.org/wiki/Azolla_event https://en.wikipedia.org/wiki/Azolla_event> Similar mechanisms have been proposed for addressing carbon sequestration goals in the present, e.g., "CO2 sequestration by propagation of the fast-growing Azolla spp. " <https://pmc.ncbi.nlm.nih.gov/articles/PMC8520330/ https://pmc.ncbi.nlm.nih.gov/articles/PMC8520330/>.
maxbond 1y ago
It could also be the opposite of a carbon capture mechanism is the detritus if those algal blooms are broken down by archaea and turned into methane, which could then return to the atmosphere. Methane is about 30 times more potent a greenhouse gas than CO2.

samirillian 1y ago

Common problem in man-made lakes. When you create a lake by damming a river it creates perfect conditions for lamination, deep narrow and filled with agricultural runoff. When they pull the plug on these dams all the de-oxygenated water flows out the bottom, basically just dumping unbreathable water into the river killing off the more sensitive fish, eg trout die catfish live, and smelling like a million firecrackers.

joek1301 1y ago

I know they aren't the point of the article, but the photos are absolutely breathtaking.

fellowniusmonk 1y ago
It's impossible to take a bad picture of crater lake, it's still the single most photogenic anything I've ever seen, there may be equals but nothing superior.
- nullstyle 1y ago
  If you feel this way, i recommend you go visit alaska; even just hiking hatcher’s pass on a good day outweighs crater lake in beauty for me.
- chihuahua 1y ago
  I feel like there are lots of places in Central Oregon that are on the same level. Anything near the 3 sisters - McArthur Rim Trail, Highway 242, McKenzie River, Clear Lake, Sparks Lake. And Newberry Crater - it's like Crater Lake, but without the crowds. You can drive up to the top of East Paulina Peak and you're probably the only person up there. The Great Obsidian Flow is nearby. And there's a trail going all the way around the top of the crater. You can spend 2 hours riding a MTB along that trail, and probably meet 0 other people.

ravedave5 1y ago

There weren't even fish in the lake until 1888, it's likely this has occurred more than once in the past.

ericmcer 1y ago
I am not sure if they still plant fish at Crater lake. If you have spent much time fishing you will pretty quickly learn that almost every accessible lake in the US is regularly stocked with fish. I would say the "native" freshwater fish population is so decimated at this point that if you want to catch something you either seek out inaccessible places that have seen little human contact, or you follow the fish plantings and catch planted fish. The idea of a lake that thousands of humans regularly access having a healthy ecology seems far fetched.
- margalabargala 1y ago
  They do not stock the lake anymore, no. The fish currently in it are considered invasive by the park and there are no catch limits. It's odd the article poses this as a "problem" in an article about Crater Lake, where uniquely among lakes this "problem" is most likely to just fix the other problem. Kill all the fish in the lake and the lake is better off.
  - maxbond 1y ago
    It won't selectively kill fish, it'll kill frogs, turtles, algae, and anything else that lives in the water which isn't a bacteria or archaea capable of living in an anoxic environment. Possibly also the predators of those species which live on land.
    - margalabargala 1y ago
      > it'll kill frogs, turtles, algae, and anything else that lives in the water which isn't a bacteria or archaea capable of living in an anoxic environment That's a bit dramatic. Frogs, turtles, salamanders, etc, can breathe air. The only predators are birds, who can find food at any of the many other lakes in the area. Crater Lake's geography is essentially unique among lakes that may be having this issue. There is a near-total lack of native fauna that would be affected by an anoxic event.