February 12, 2020

Extremely Favorable Water Supply Outlook for this Summer

If you enjoy drinking water, keeping your plants green, and appreciate an agricultural bounty--there is good reason to smile.  The water outlook is exceptionally favorable for this summer

As noted in my previous blog, the last two months have brought far wetter than normal conditions over the region, including a restored snowpack.

The latter is illustrated by the SNOTEL snow water equivalent map, which indicates an overall state snowpack a bit more than 100% of normal. 

The City of Seattle reservoir storage is way above normal-- in fact as high as the usual peak reservoir level in May and early June (and Seattle has been letting out plenty of water to prevent dams from being overtopped).   Similarly bountiful conditions are found for the Everett and Tacoma water systems.

But the biggest water challenge is always on the eastern slopes of the Cascades, water that supplies the huge agricultural industry of the region.    One key source of water is the Yakima River and its associated reservoir system.  As shown in the graph below, the Yakima storage system went from well below normal in November to above normal today, with the water level now as high as early April last year.

The other major sources of water for Columbia Basin agriculture is the Columbia River, whose water run-off volume for April to September is predicted to be 106% of normal by the National Weather Service's Portland River Forecast Center.  All good.

And the precipitation is not over.  The latest UW WRF model 180 h forecast of accumulated precipitation (below) suggests 2-5 inches of water content in our mountains, with several feet of snow above roughly 4000 ft.

And to top it off the latest NOAA Climate Prediction Center three months forecasts are for normal temperatures and normal to above normal precipitation over the region.

The bottom line is that we are in exceptionally good shape regarding water for the upcoming summer and early fall, with no sign of drought or water shortages.  With well-filled reservoirs, lots of snow, and much more precipitation in our near future, there is little likelihood of water issues later this year.


  1. Ahh. . . good water news in a virtual sea of world problems!

  2. I'm glad our reservoirs are full! One thing I wonder is how much we depend on snowpack from the winter melting over the spring/summer for human water needs in the summer/fall (drinking water, agriculture, etc)? Could our reservoirs system, if full at the end of the spring, supply all human needs for summer and fall if there were somehow no snowpack or precip after April? i.e. what percent of our human needs do reservoirs play (if full)?

    1. Yes. That was answered in 2015 when we had virtually zero snowpack. Precip is what matters for the vast majority of the state.

      The Yakima is a whole other can of worms. They have been fighting over water there for almost a century.

      More here - https://cliffmass.blogspot.com/2015/10/did-pacific-northwest-pass-global.html; https://cliffmass.blogspot.com/2015/06/the-super-heroes-of-2015-northwest.html; https://cliffmass.blogspot.com/2015/03/will-seattle-have-enough-water-this.html

    2. We already know. In 2015 there was little to no snowpack and a spring drought. The rains of the previous season that filled the reservoirs were more than enough for human needs (albeit with some strict water restrictions) until the Fall rains returned (early that year too thankfully).

  3. But but but but.... we were in a desperate DROUGHT according to the drought index well into November! That we were declaring emergencies in the central cascades by the governor because, due to human (solely) caused climate change that this new normal was solidly in place and we were irretrievably stuck in catastrophic drought sure to kill commerce in the Methow Valley and along the Columbia River Valley. The sheer number of salmon that wouldn't be able to make it up to spawn because there would be no water!

    How could it possibly be that there is plentiful water?

  4. Amanda, we had little to no snowpack in the Cascades a few years back (El Nino year, I believe), and there were minimal water problems through the summer into the Fall. But there was a ton of screaming about the upcoming disaster, as per usual.

  5. To continue with Amanda's thought, how much of out water supply comes from aquifers that are likely being recharged from this bounty of precipitation?

    Since we have more water wells in the South Sound than central north or Kitsap peninsula, are we less dependent on snow melt?

  6. hey, cliff, tell us we will be ok in CA and that joseph and the pharaohs just got to get together to make everything alright here

  7. Possibility for thunderstorms on Sunday? I'd like to hear something about it on the next blog!

  8. The salmon returns this year on most streams in Wa and lower BC were quite low and most of them were little guys in the streams and tidal areas 4 years ago.

  9. Who else is waiting for those warmer days, where you can actually step outside in T-shirt and Shorts and fell fine... Ahh, the thought of summer...

  10. @Eric Lots of Chicken Littles in our state primed to declare planetary destruction when we get an inch more rain than usual or an inch less.

  11. Excellent! Now I want a nice SUNNY, WARM, mostly DRY SUMMER this year! :)

  12. Despite a dryer-than-average January, precipitation that Montana desperately needed and that helped increase snowpack levels in most of the major river basins arrived in February. In most of Western Montana, the Snow Water Equivalent (SWE) levels as of March 20, 2023 are around typical for this time of year, with somewhat less snowpack in the St. Mary and Milk, Kootenai, and Bitterroot basins. SWEs are currently above 100% in the Madison, Gallatin, Helena, and Smith-Judith-Musselshell basins.

    Sydney water borers


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

High Pressure and the Northwest's White Affliction

 The visible satellite image this morning was stunning. Low-elevation clouds covered nearly all of Washington, except for the highest elevat...