November 03, 2015

Refill of the Region's Water Supplies

During the last few days of heavy rain, our reservoirs have filled with enough water to supply the Puget Sound region's needs for the next three months or more.  Furthermore, our mountain snowpack has gotten a good start for the season.  And the next few weeks will bring a great deal of precipitation.

Water refill time is here.

Let me begin by showing you two stunning figures:  the water storage for Seattle's two reservoirs: Chester Morse and Tolt.  At Chester Morse, the reservoir level has jumped nearly 13 feet, returning to the levels of late-July (more than 3 months ago, including periods of heavy water usage).   This time of the year that much water could supply the region for an even longer period.  Translation:  the water worries of Puget Sound country this year are over.

The Tolt reservoir also had a big jump, back to the levels of mid-August.

Or we could look at one of the key reservoirs supplying water for the Yakima Basin, Keechelus, which is now approaching normal levels after being well below normal.

The impact of this major wet event was profound.

It is not always appreciated that although we have many days with precipitation during our winter season, most bring light rain that only add marginally to our water resources.  The real business is done by roughly a half-dozen big wet storms, generally associated with atmospheric rivers.  And this weekend, we had one of them.

Let me demonstrate this to you by looking at the cumulative precipitation over the best year at Seattle Tacoma Airport with the red line being the observed precipitation and the blue showing the average amounts.  The last year had just below normal precipitation (not a precipitation drought).  Note how the observed precipitation is staircased, with most of the precipitation occurring in 5-10 big events.  This is very typical.  Most of the refill of our reservoirs occur over roughly a half dozen events.  Light rain events are not that productive, with a lot of the water evaporating from plants and the ground.
Plenty more is coming.  Here is the cumulative precipitation forecast through next Wednesday evening.  Plenty of water over the Northwest.   Even California gets some of the wet bounty.

And now for something really amazing.   You like snow in the mountains?  Who doesn't?  Here are the NOAA snowdepth plots for October 29 and November 1 (10 PM PST).    We went from virtually nothing in the Cascades to several inches to roughly a foot in the higher elevations of the north Cascades,

The snow water equivalent of the snowpack (below) shows a similarly impressive change.

Our region is now filling up from the water service station in the sky and it looks like the next few weeks will be typically wet.

The Northwest Snow and Avalanche Workshop is this weekend (November 8th).  Lots of great talks and a big crowd of snow lovers.  For more information on the meeting and how you can attend, go here.


  1. This is great news. I can now return to washing my garbage, making it fit for recycle.

  2. With the winter forecasted to be warmer, is this snow surprising? Or is this typical and doesn't necessarily mean we'll still get a lot of snow in the mountains?

  3. I always enjoy your analysis of the weather and your commentary, however the following statement, which perhaps accurate for 'this time of year', I think may easily be's a long way to from now until October 2016 when it comes to water security.
    "Translation: the water worries of Puget Sound country are over."

  4. But how can this be? The doom and gloom experts at the Department of Ecology told us it was drought panic time?

    I guess even the so called experts have to admit that this climate and weather thing is not as simple as their computer models with which they assured themselves. Maybe that is also why we have had nearly 20 years of lesser temperatures than the same doom and gloom experts have predicted with their GCMs?

    Funny how it takes experts a lot longer than average person to say to themselves "maybe my assumptions are wrong?" I bet the willingness to reflect on the accuracy of models is related to how much grant money the modeler has received. Or on how many nice vacations the modeler has taken to COP conferences. Copenhagen! Bali! Lima! Paris!

  5. To JeffB... the rains have only improved conditions in 1/3 of the state. The other 2/3rds, per the web page you referenced, are still in drought, and the winter snow forecast isn't great thanks to the El Nino.

    No need to attack the modelers. They are following the science until the data convincingly changes, as they should.

    The average person can change their mind with their underwear.

  6. Dr. Mass,

    What's this I'm hearing about a major storm 10 days out? Too soon to get excited or is this looking like a real possibility?

    -- Mike B.

    1. I'm not an expert by generally 10 days out is a bit far out to get excited. I'd wait until the experts start keeping an eye on it because of model consistency...but even 3-5 days out the models can change their minds. Depressing, I know....I love stormy weather!

  7. Following the science are they? No scientist I know would use the terminology "drought keeps grip on state", especially after the precipitation this fall. But frankly they would never use it, ever.

    The very concept that Western Washington is in a "severe drought" (including Seattle and their watershed) is so inaccurate it enters into a very troubling area. That is what the map is saying at this very moment (my guess is they change it tomorrow). Anyone wondering why people are tuning this stuff out need look no further than that website and map. How could anyone justify the fear-mongering they are doing? My goodness just go one step further and look at the usgs stream maps. But like anyone needs a stream map to tell them what they just saw.

    Cliff has been one of the few - no make that the only - scientist I know telling the truth on the issue of "drought" this year (which as he notes above, was not, and never was, a precipitation drought). Why is that?

  8. I think we worry too much about water around here. We in the west have lots.

    Change of topic. Cliff, would you like to discuss plants/frost in an upcoming blog? I have a question: Based on the dew point, how well can I predict frost risk in my local area on a clear night? For example, if the dew point is 35 degrees F, can I safely say to myself, "the fog will form about 35 degrees, the cooling will stop, and the remaining plants are OK tonight"?

  9. Hoorah! Everything will be fine now.

  10. We need a State of the Blob address Cliff!

  11. Drought isn't simply a function of annual rainfall. What this year has taught us is that it depends on how the rain falls and potential evaporation.

    Yes we had close to normal rainfall on an annual basis.

    Yes we have a severe drought because that water isn't available because of how, when and where it fell. And its been warmer than usual.

    Also, the NWS Climate Prediction Center shows us drier and warmer than usual from Jan through May.

    Sure, we're improving, but it's too early to stop worrying about drought. The amount of snow in the mountains come Spring, and next summer's temperatures, will determine if we're "healed" or are still in drought.

  12. And that is exactly where we are today with the word “drought”. It no longer means: “A period of below-average precipitation in a given region, resulting in prolonged shortages in its water supply, whether atmospheric, surface or ground water”. You know, the actual definition.

    No, now it means whatever someone wants it to mean, often to push whatever agenda they have. A couple of weeks with no rain in a temperate climate? Drought. A year with normal precipitation, with full reservoirs? Drought. A scary forecast about what is imminently going to happen (that often does not come to fruition)? Drought.

    Drought is increasingly an Orwellian term in our lexicon. Fitting with Orwell, it is visceral, highly charged and powerful. It is used, more often than not today, to garner pageviews or to affect behavior. It rarely seems to represent actual truth or actual statistics, except when I come to this blog.

    If there is anything to be worried about today, that would be it to me.

  13. Official American Meteorological Society Definition:
    A period of abnormally dry weather sufficiently long enough to cause a serious hydrological imbalance.

    Drought is a relative term, therefore any discussion in terms of precipitation deficit must refer to the particular precipitation-related activity that is under discussion. For example, there may be a shortage of precipitation during the growing season resulting in crop damage (agricultural drought), or during the winter runoff and percolation season affecting water supplies (hydrological drought).

  14. Thanks Cliff. That is a fairly subjective definition though of something that would seem reasonably objective given the measurement technology we have today. What defines "abnormally"? What defines "sufficiently long enough"? What defines "serious"?

    You are into numbers. You cite statistics. It's why I come here. That definition as applied could mean virtually anything, at any time, depending on the observer and depending on the day. I just picture two people on a sunny day, with one saying "It's a drought!" and another saying "No its not!" (For your entertainment, I would likely be the one saying "No its not!").

    So... statistically here... what is "abnormally". A standard deviation? 2? And measured from what point? What is "sufficiently long enough", in quantitative terms? Or am I beating my head against a wall here.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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