[benj111]

This quote gets me thinking about how snow is treated in this system.

It isn't like water in a stream because it stays where it is. It isn't like a reservoir or aquifer because the water isn't trivially dispatchable.

I suppose it depends where the snow is, some could be 'permanent', some seasonal melt, some gone by next week.

So really we should be differentiating the different types of snow?

[mturmon]

Snow is really important. It is quantified as “SWE” or snow water equivalent, the amount of water that would be released when the snow melts.

SWE is monitored by satellites, aircraft, and by in situ measurements like from snow pillows. In California, the state DWR tracks SWE to estimate reservoir influx.

More: https://aso.jpl.nasa.gov

[benj111]

Thanks, didn't realise snow pillows were a thing.

https://en.m.wikipedia.org/wiki/Snow_pillow

[gwbas1c]

It all melts.

I trust that the experts know the difference between permanent snow and annual melting. They use satellite pictures to determine how much water will be available after it melts.

Edit: If someone knows more about the planning process than I do, please chime in.

[benj111]

To be pedantic:

You say "It all melts", and then "I trust that the experts know the difference between permanent snow....".

I hypothesised satellite photos, I'm not sure if depth of snow is relevant for more than just volume, and whether you could get good estimates of depth (and density???) from a satellite.

[gwbas1c]

A few years ago I read an article on Hacker news about the drought. It discussed the experts looking at satellite photos and then climbing to mountain tops to perform more detailed measurements.

Don't forget that modern satellites are topographical with a high degree of accuracy. We can use satellites to learn snowpack depth.

This is how we know that the aquifers are depleted because the satellites measure elevation above the aquifer.