April 10, 2013

Northwest Water Supply Outlook for the Summer and Fall: Looking Good

As the summer and fall months rapidly approach, the natural concern is about water:

Will the Northwest have enough to get through our dry summer and early fall?  
Will there be enough water to maintain stream flow for fish and to support the large (and growing) agriculture east of the Cascade crest?
Will our demands have enough water for effective power generation and modest rates?

We now have enough information to answer these questions:   We are in good shape.

Let's begin by looking at the current state of the snow pack, or more specifically the snow water equivalent (SWE)--also known as snow water content.  Snow melt is the main source of water during the dry part of the year.   As seen below, Washington has near normal snow water content, ranging from 129% in the Olympics, to roughly 110% in the Cascades, and approximately 85% in eastern Washington.  Oregon and Idaho are a bit below normal, with only the southeast corner of Oregon being seriously dry.  We can thank a wet November and December for putting the NW in a good position.

California is in trouble with Sierra snow water contents between 50-70%. 

Based on the snow pack observations on April 1, the USDA has estimated spring and summer stream flows (see below).   Looks good for the Columbia River drainage and most of the streams draining the west side of the Cascades, and decent (70-90%) for most of the remainder of our region.  Again, only SE Oregon has problems.  Not good for the SW U.S.

The National Weather Service Drought Monitor shows that most of Washington has normal or greater soil moisture content, with progressive drying as one trends to the Southwest U.S. and the Great Plains.

So considering what is on the ground now, Washington State is in good shape for the summer.   But it is better than that!   The next week is going to be cool and wet, with considerable additions to the snow pack.

Here is the WRF model prediction for the next 72 hours. Large amounts of snow in British Columbia (good for the Columbia River!) and in the central and northern Cascades.

 And the next 72 hr?  (see below) Moderate snowfall throughout the regional mountains.  Think of this as "topping" our watery gas tank.

In summary, Washington State and British Columbia will have normal water resources this summer.  Most of Oregon is in decent shape, except for the southeastern part of the State.  But California and other southwest states have a problem, and I understand the water allotments to California farmers are already being reduced.  Folks may complain about our cool, wet weather during the winter, but it brings a great gift--large amounts of water to support recreation, our fisheries, power generation, and a great agricultural enterprise.


  1. I remember a few years back when Governor Gregoire worried publicly about a drought. I laughed and laughed and laughed. This is Western WA. Some people just cannot resist a fairytale crisis.

  2. FYI to JeffB, Governor Gregoire was the Governor of the entire state. Eastern WA and Western WA.

  3. And the drought did not materialize in Eastern WA either.


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