US west coast braces for ‘atmospheric river’ as storm brews | Hacker News Reader

US west coast braces for ‘atmospheric river’ as storm brews

theguardian.com

26 pointsWalterGR26 comments

I believe I read somewhere that massive rains like this don't help with the drought situation as much as you might think because it's just too much rain in too short of a time and a lot of it runs off into unproductive places (rather than getting stored in lakes, dams, etc.). Is that idea accurate?

That makes sense but I remember the drought of 2016 ended pretty quickly during one of these storms. Reservoirs went from 20% capacity to 100% in a few days and excess water had to be released downstream.

That one put a ton of snow in the mountains as well, this one is going to be too warm to put the same amount of snow into the mountains (although there will be some). Snowpack functions as a massive reservoir, so that matters.

That being said, 8 inches of liquid precipitation in 2 days isn’t as good as 8 inches if liquid precipitation over 2 weeks, but it’s still a boon to water systems.

Sort of. It's true for the urban and coastal areas - in fact, there's a landslide & flash flood watch for the CZU burn scar and most of the North Bay right now.

Large parts of the Bay Area mountains drain into captured reservoirs, though. The eastern slope of the SF peninsula all drains into Crystal Springs reservoir. Most of the inner Berkeley Hills & Briones Regional Park drains into the San Pablo reservoir. The mountains between Oakland and Danville drain into Upper San Leandro reservoir. Sunol and the lower Tri-Valley drains into San Antonio reservoir. Henry Coe State Park and the surrounding ranchlands (which is huge, bigger than all of the urbanized Bay Area put together) drains into the Calaveras and San Luis reservoirs, as well as Anderson & Coyote Lakes.

Anderson Lake, last month, was at 3.5% capacity. So yes, this is a very welcome rainstorm, and much of it will be captured for municipal water. If it came on the heels of a very wet season (like the 2017 atmospheric river that flooded Coyote Creek and threatened to overtop Anderson Lake), they yeah, it'd be wasted, but that's not the situation today.

As far as I can tell, the Crystal Springs reservoir has been approximately full for years. I don’t know whether SFPUC has the ability to pump from it to other reservoirs, but I don’t think it has capacity to hold much more stormwater.

Data from this summer:

https://almanacnews.com/news/2021/07/12/state-expands-drough...

Apparently Crystal Springs is intentionally being kept full in case of wildfires. It's the emergency reservoir for San Francisco and northern San Mateo County.

Anderson is empty because the dam needs replacing. The reservoir is essentially offline till a new dam is built. It's really too bad that it was the largest capacity lake in Santa Clara County.

From the Hacker News guidelines: "If they'd cover it on TV news, it's probably off-topic."

https://news.ycombinator.com/newsguidelines.html

Ehh, I think this an "atmospheric river" is an interesting phenomenon so it's on topic for me. I had never heard the term before[1].

[1]https://en.wikipedia.org/wiki/Atmospheric_river

What a storm for this parched land.

As a former Californian the storm is tiny by East Coast standards but I sure hope it delivers

Raining hard in SF right now!

Small town north of Truckee. Predicted to get 6-7” today. We are at 2.4” according to my westher station.

> storm is tiny by East Coast standards

OK but natural water flow is adapted to local conditions, over generations.. a disaster is something that doesn't fit capacity..

I had a similar aha moment as you when casually talking to a stranger about the rain in California - she looked dismissive and said "I am from Michigan" and walked off !

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