Sierra Snowpack Could Be Gone In 25 Years

[maverick]

Let's stay on subject, please. Any further off topic post will be deleted.

[erutan]

It's all pretty on topic for an "anything goes" subforum with an article about the impacts of climate change that IMO. I was referring to this section as being OT (in regards to HST in general), not my post. I don't anything I posted has violated the TOS here which is the other requirement.

Your post contains the line:

The authors framed their paper as a “call to action.”

We've been talking about the ramifications of this possible future, along with reasons why it'll likely come to pass. What would the scope of discussion be limited to? Specific policy proposals for redistribution/catchment of water in California?

The fact that the west is overextended on water use has been known for quite some time. You can go back to John Wesley Powell's research in the 19th century - Cadillac Desert is a good narrative read. The slow death of the Colorado & depletion of aquifers are as impactful or more than the loss of snowpack of the Sierra in terms of water security - actually trying to picture what the Sierra Nevada will look like in the future seems more relevant to the board.

It could be split off into a ‘impacts of loss of snow in the Sierra Nevada and why that’s likely to happen’ thread if that’d be cleaner.

[SSSdave]

snippet:

Scientists and water managers say that at some point California’s snowpack could simply disappear. This would leave the state without the crucial spring and summer melt-off that fills rivers and streams, nourishes plants and animals, and provides a huge chunk of the water supply. It would also be devastating for the ski industry. This snowless future, according to a new study led by researchers at Lawrence Berkeley National Laboratory, could arrive in California’s Sierra Nevada in as soon as 25 years. The study is among many to detail the decline in snow, but it’s unique in synthesizing decades of research to nail down exactly when the snow might be gone. And it offers a timeline that is alarmingly short.

(posted earlier on a ski forum)
The headline overstates the information source probably because the above better serves as click bait. Also urban newspaper reporters do not tend to be mountain people so tend to understand weather and mountain subjects like this poorly.

Generally atmospheric temperatures change 3F (1.8C) degrees per 1000 feet. Current predictions for 2050 show a change of just 1.6C higher. But lets go way higher. A change of 4C at the Tahoe latitude would mean a change of average storm snow levels from about 6,000 feet to 8200 feet. That would of course greatly affect Tahoe ski resorts making conditions at the base of Kirkwood similar to those now at the base of Squaw. The Northern Sierra would see mostly rain storms in winter while there would still be considerable snow over much of the Southern Sierra because those mountains have vastly much more square miles of higher elevations above 8,000 feet. Thus the headline more properly should be:

Snowpack at Tahoe could disappear in just 25 years

California Physical Map and California Topographic Map

https://geology.com/topographic-physica ... rnia.shtml

Note Lake Tahoe is at, 6,250 feet above sea level while the High Sierra has many peaks over 13k and 14k. Also the reporter makes it sound like we would be losing water. That may be true if the northern jetstream changes to the north putting California in desert latitudes but if snow just became rain, it would not make much difference with what flows into reservoirs. Each winter most of the Sierra north of Tahoe is already in the rain zone and reservoirs like Shasta or Oroville have no problem filling up. It just won't happen during summer.

[bobby49]

if snow just became rain, it would not make much difference with what flows into reservoirs. Each winter most of the Sierra north of Tahoe is already in the rain zone and reservoirs like Shasta or Oroville have no problem filling up. It just won't happen during summer.[/color]

It may not make much difference in the total amount of water flowing into reservoirs. However, having the snow just hang there in the mountains as a natural reservoir and very slowly melt avoids the problem of overfull reservoirs in one season and dry reservoirs in another season.

[Wandering Daisy]

The bulk of the snow melts much faster than a "slow melt". That is why we have high peak flows in streams fed by snow. If it warms of quickly in the spring and the ground under the snow remains frozen there is no soaking in the ground and the snowmelt produces more runoff. The largest floods have been in January through March when warm rain falls on the snow and melts it so not only the rain produces runoff but snow too.

The later season (May-June) slow melt from the higher altitudes is much more important to the fishery and wildlife by maintaining permanent streamflow than it is to the water storage system in the Central Valley.

[erutan]

I'll third that snow melting off and gradually releasing water makes a difference. We don't have a lot of good places to build new reservoirs - building dams was (bipartisan) pork senators loved until Carter snipped it. Some of the dams from the 70s have been removed because of how they impact flood plains etc. Kings Canyon was almost dammed in the 50s. Yosemite Valley would compliment Hetch Hetchy I guess. More reservoir capacity would help, but relying solely on rain makes things a lot less predictable. We could basically get rid of Lake Powell at this point due to the lack of snowpack in Colorado and just have the water from it go into Lake Mead (this was an interesting read from last August: https://www.newyorker.com/magazine/2021 ... ake-powell).

I find it amusing that someone was stating our reservoirs have had no issues filling up over the past decade...

Aside from reservoir capacity there's the ecological impacts of having areas dry out in the summer outlined earlier. The retreat of glaciers and permanent snowfields will continue until they're basically non-existent, then all it will take is a couple years without heavy winters to decimate forests (which doesn't seem very unlikely).

Driving through the central valley a few days ago it was interesting how the focus has shifted from dams to "wasted" river water. There were a number of signs along the vein of "democrats are wasting our farm water, 78% of CA river water runs into the sea". Which is sort of amusing as the Kern has been killed already. I assume they're focused on the Sacramento river and want to just redirect water from the delta down to their monoculture farms, which would be a far easier political solution than building a bunch of new reservoirs. Running aqueducts down from the Eel or Klamath would be another option I guess. It's amusing that they feel the water is "theirs" and for farming, given rivers existed far earlier than humans deciding to grow a bunch of water intensive crops in the desert because of the centrifugal pump.

Sea level rises obviously impact coastal infrastructure, but San Diego is well situated with a desalination plant and nuclear and ~75% of the state's population lives in coastal counties. We're in much better shape than AZ, which will lose a huge chunk of their agriculture in the coming decades. Agriculture in general will shift northwards as growing seasons lengthen there and shorten to the south, so trying to maintain some status quo probably isn't a great focus anyways.

We already had a year with basically zero snow pack at any elevation in June/July. There's a difference between "it will never snow"

[erutan]

https://xkcd.com/1732/

Webcomic, but it illustrates the overall climate temps in what we’d consider human history (from a civilization standpoint), and going back a bit further. Humanity can obviously survive outside a +-1C range, but what we consider modern civilization is going to be heavily impacted. Supply chain issues now are nothing.

-4C didn’t just have colder winters and nice summers on the east coast. Boston was under a mile of ice. Air temps impact ground temps, compound how snow/ice melts or doesn’t melt etc. 1.6C by 250 is still quite significant and 2.5-3C by the end of the century will leave large regions uninhabitable (and others more habitable, watch out Canada, the southwest is thirsty and looking for farmland). It’s not outside the historical range of temperatures reached in pre-history, but it’s the rate of adjustment *is* unique and that is sure to have some unpleasant side effects as well.

[SSSdave]

[SSSdave]

...I find it amusing that someone was stating our reservoirs have had no issues filling up over the past decade...
Aside from reservoir capacity there's the ecological impacts of having areas dry out in the summer outlined earlier. The retreat of glaciers and permanent snowfields will continue until they're basically non-existent, then all it will take is a couple years without heavy winters to decimate forests (which doesn't seem very unlikely)...

Actually that is not what I wrote.
SSSdave >>>"The Northern Sierra would see mostly rain storms in winter while there would still be considerable snow over much of the Southern Sierra because those mountains have vastly much more square miles of higher elevations above 8,000 feet. Thus the headline more properly should be: Snowpack at Tahoe could disappear in just 25 years...
Each winter most of the Sierra north of Tahoe is already in the rain zone and reservoirs like Shasta or Oroville have no problem filling up. It just won't happen during summer."...

It's just that those responding made it read like I generalized so as they clarified why a summer snow pack has an advantage. Details I of course am well aware of. So yeah there would be more winter run off in all areas though far less than the article headline paints. And indeed water managers would need to tweak their strategies in the south.

[erutan]

I remember back in 2013-2015 Shasta was pretty low, it's currently at 47% of historical value at the moment and that's after a wet summer and a major storm (as your % of rainfall for the last six months graphic shows): https://cdec.water.ca.gov/resapp/ResDet ... ?resid=SHA The majority of California is in D3 - Extreme Drought at the moment https://www.drought.gov/states/california with a drier than average winter expected in socal at least (~60% of annual precip) and reservoir health has fluctuated due to droughts in the past few decades.

Norcal should be impacted less by snowmelt as you say (though there's certainly some around Shasta/Lassen/Trinity Alps), but we're going to be more likely to swing between massive storms that dump large amounts of rain at once (this is happening around the country and is bad for a number of reasons) and droughts. Warmer temperatures would impact evaporation rates as well though that's probably negligable.

California as a whole will be waaaay better off than the inland SW, just due to proximity to wet air from the pacific and the pacific itself. I'm pretty sure something will be sorted out, even if it requires some decently large scale migration. The Central & San Joaquin valleys are already hitting issues with aquifer depletion, but as temps warm crops will shift northward- central california used to be too cold to grow figs etc a generation or so ago, which now do fine there. Mangos will be a plus (though regional collapses in Cental America will impact us). 395 is most likely going to bled dry by LADWP with their junior water rights.

I'm less concerned about California's water infrastructure as a whole as I am about the Sierra Nevada themselves.

What the modeling from that paper showed was that by 2047 there’d be 5 year stretches where the range had 0-5% snowpack. By 2060 decade long stretches would be common. This year the Tyndall Creek ranger (who has been there since the 90s) said it looked like October when we chatted in late spring. That’s just one year in that range, and two years out from a very heavy winter in 2019.

The climate is a complex system, and models aren’t anywhere near 100%, but the vast majority of the near past work has been massively optimistic. Whether it’s 2040 or 2055 it’s still the death of the range below 11.5-12k. But I guess some dude on a ski forum has way more data points to work from? :/