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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

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?

refurb 5y ago
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.
- topkai22 5y ago
  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.
nostrademons 5y ago
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.
- amluto 5y ago
  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.
  - deleted 5y ago
    [deleted]
  - nostrademons 5y ago
    Data from this summer: https://almanacnews.com/news/2021/07/12/state-expands-drought-emergency-to-santa-clara-san-mateo-counties 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.
- Fatnino 5y ago
  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.

refurb 5y ago

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.

topkai22 5y ago
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.

nostrademons 5y ago

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.

amluto 5y ago
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.
- deleted 5y ago
  [deleted]
- nostrademons 5y ago
  Data from this summer: https://almanacnews.com/news/2021/07/12/state-expands-drought-emergency-to-santa-clara-san-mateo-counties 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.
Fatnino 5y ago
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.