Why the Washington Drought Emergency Should Be Dropped Immediately

It is time to clear the air.   

To definitively correct misinformation being pushed by a Washington State agency, the Seattle Times Climate Times Climate Lab, and some amateur YouTube channels.

The claim that this summer represents a DROUGHT EMERGENCY for Washington State.   

It is simply and demonstrably false.

In a previous blog, I showed that our reservoirs are fuller than normal, soil moisture levels are good, our annual precipitation is at or above normal, and that current crops are doing well. 

But like some vampire, the drought claims can not be killed so easily.   

In particular, the media, YouTube amateurs,  the State Department of Ecology, and others are pinning their drought claims on the Yakima River drainage and this year's low snowpack.

Below, I will demonstrate why they are very much wrong. 

Yakima and Kittitas counties, through which the Yakima River flows, are relatively arid locations, being located in the rain shadow of the Cascade Mountains (see below).

Only with substantial irrigation can they provide the agricultural bounty for which they are well known.

This irrigation comes from two sources.  

Much of Yakima and Kittitas agriculture gets its water from the Yakima River, with some contributions from the Columbia on the eastern side of the area (see map below).   Everyone agrees that the Columbia will have plenty of water this year, so there is no suggestion of drought for the majority of the irrigated land in eastern Washington (blue, purple, and yellow colors below)

The Yakima River drains off the Cascades, starting near Snoqualmie Pass, and is also fed by a few tributaries, such as the Cle Elum, Teenaway, and Naches rivers.

These rivers are mainly fed by mountain rain and melting snow.  Since most of the precipitation falls in winter and spring, while most of the irrigation demand is during the dry summer (particularly July and August), water storage is required.

One source of storage is the Cascade snowpack, which does most of its melting in May and June.  Thus, snowmelt is only a short-period source of water... a fact that will be important later.

And then there are the Yakima River Basin reservoirs (see below), which are filled by both rainfall and snowmelt.

And finally, there is spring and summer rainfall, which is modest in this region.

To fully supply water for all agricultural and human needs of the Yakima irrigation district requires about 2.3 million acre feet for April through September.    The reservoirs can hold about 1.1 million acre-feet, or roughly half what is needed.

The remainder must come from the river flow, supplied by either mountain rain or snowmelt.   

A big issue is timing:  only the reservoirs can supply a large amount of water during mid-summer (July and August) when demand is greatest.  

Keep this fact in your mind...it is crucial.

Now, let's consider the water situation this year.   The annual precipitation was actually wetter than normal over and near the Cascades (see difference in normal during the water years from October 1 to  May 6, below).  So plenty of water falling from the sky.

But much of this precipitation was associated with warm atmospheric rivers and substantial amounts fell as rain, particularly at lower to middle elevations.   Particularly strong atmospheric river events occurred in December (which produced substantial flooding) and March.

Because of the warmth of those atmospheric rivers, the snowpack was below normal this season over the central and southern Cascades, with the Yakima Basin topping out at around 50% of normal (see below).  Not zero, not 20%.   This is going to be important as well.

The substantial precipitation and the wise actions of those running the Yakima reservoirs have led to the Yakima reservoirs filling well in advance of normal.   Filling early without the need for snowmelt.    

Check out the figure below, which shows the water storage this year (blue line) compared to normal (red line).  Stunning.  We are already above the normal mid-June peak!

The Yakima Reservoir storage will remain topped off for several more weeks.  Why?   There is still considerable snow left to melt at higher elevations in the Cascades during the next week or so (see below).

.And the current model forecasts indicate substantial precipitation over the region next week (see totals through next Saturday).

There will be plenty of precipitation and snowmelt to keep the Yakima Reservoir system topped off through the end of the month.  No drying heatwaves are forecast during this period.

With Yakima Reservoir full in early June, there is a near certainty of sufficient water for Yakima County agriculture this summer.

I am not speculating....I checked.   Full reservoirs starting the summer are associated with ample water for agriculture in Yakima and Kittitas Counties.  There have been no examples of serious agricultural water issues for years in which these reservoirs start off the summer full. 

So how could the Department of Ecology and others get this so wrong?

They did not consider several unusual aspects of the past year.   

We started off with very low river and reservoir levels last fall.  But then we had crazy heavy warm rain in December, which caused a massive increase in river levels on both sides of the Cascades.   To illustrate, the figure below shows the flow on the Yakima River at Umtanum over the past two years (see below, black line).  Then, in March, another major event occurred.  Both were at record levels (dark blue lines)

Knowing about the low snowpack, the Yakima system water managers saved a portion of the huge influx of water,  pushing storage WAY above normal.  Very wise.

Normally, some of the melting snowpack is used to fill the reservoirs, but because of the heavy rain, it was not needed.   Thus, the melting snow could be used simply to keep the reservoir topped off and support reasonable flows.   

Because of the above-average precipitation last winter and the full reservoirs, we did not need to have a normal snowpack this spring..... 50% could do.   And the substantial rain also provided soil moisture west of the Cascades.

Those falsely calling for a drought emergency love to note that reservoirs can only hold about half the needed water for Yakima irrigation, and thus, they suggest that we need 100% snowpack to get through the summer. 

False!

But they are thinking too simplistically.  During the spring and early there is still substantial precipitation and water draining into the system, providing water for irrigation and other uses.  And we never use 100% of the snowpack water, with substantial amounts running into the sea.   Don't believe me?  Here is the average flow at the Dalles on the Columbia River.

A snowpack with 50% of normal snow still has a LOT of water.

In summary, the Drought Emergency Declaration by Washington State should be dropped immediately.  

Washington State residents deserve accurate information.  Washington agriculture should not be undermined by ill-advised, unscientific declarations.