The headlines and warnings about drought conditions have been increasingly strident, such as the Seattle Times article on low-water levels for the Yakima River Reservoir (see below).
Considering the tendency of the somewhat subjective and drought-extravagant Drought Monitor product, let's examine the actual precipitation numbers (below).
Over the past year, the Cascades and southwest Washington have been considerably drier than normal. But much of eastern Washington has actually been wetter than normal.
What about the summer (July 5- October 2)?
Near or slightly below normal precipitation over eastern Washington. Wetter than normal over the NW Olympic Peninsula and drier than normal over the western side of the central and northern Cascades.
The low Cascade snowpack last winter resulted in a lack of snowmelt in late June and early July.
As a result, with less snowmelt, the Yakima River reservoirs fell below normal by mid-July (see plot below of this year's storage--blue--versus normal--red).
By the way, last year (2024, green) actually had ABOVE AVERAGE Yakima storage levels. Currently, the Yakima reservoirs are about HALF of their normal levels.
There is no doubt that last winter was drier than normal. But is this due to climate change or just typical natural variability?
We can easily examine this by looking at historical precipitation over many decades.
For Washington State as a whole, the trend for annual (September to August) precipitation for 1900 to 2025 (shown below) shows lots of variability, but little overall trend.
2025 has been drier than normal but hardly record-breaking....many years have had less precipitation.
Although summer precipitation is relatively unimportant in our region (our summers are some of the driest in the nation), here is the trend of summer (June to August) for precipitation over Washington State. Moist from roughly 1940-2000, but drier during the 1930s (before climate change) and recently.
No real trend over the last century and a quarter.
I am in a position to show you this, since my group does such simulations. Here is the plot of predicted precipitation change at Stampede Pass in the WA Cascade using a high-resolution climate model driven by very strong greenhouse gas forcing (RCP 8.5 for those familiar with climate change scenarios).
Precipitation INCREASES as the Earth warms. (The green lines show the average of many simulations)
There is no long-term trend towards less precipitation over the region during the past 120 years.
Furthermore, climate models driven by increasing CO2 produce more precipitation over the region, not less.
As the planet warms, more of our mountain precipitation will fall as rain rather than snow, but reservoir systems, such as the Yakima's, can store the water no matter how it gets into the river.
It might be wise to expand regional reservoirs to save more winter rain.
Cliff, I’m a big fan of your blog and appreciate your critical comments of the media attributing a lot to climate change. But, as a resident of Cle Elum 25 miles east of SnoqualmiePass, I’m telling you the drought in the Yakima basin is real! According to the Bureau of Reclamation which operates the reservoirs at the headwaters of the Yakima, Lake Keechlus is currently at 6% of capacity and Lake Cle Elum is at 4%. I have never seen them this low! The Yakima River at Cle Elum is currently running at less than 200 cfs! I’ve been fishing this river in the fall for over 30 years and I’ve never seen it this low. Not even close.
ReplyDeleteYou have the data. What will it take to bring those reservoirs up to 90-100% of capacity?
This is the third year in a row of below normal precipitation which may be “normal variation”, But I’m guessing it’ll take a few years of above normal variation to bring these reservoirs up to near capacity. Can you quantify that? How likely is that?
Thanks for your informative and insightful commentaries on our local weather.
Steve
PS: I became fascinated with meteorology over 50 years ago as a sophomore at the UW when I took an introductory class.
"It might be wise to expand regional reservoirs to save more winter rain." In our current political situation where our elected officials can do nothing and blame "climate change", that might be too big of a push.
ReplyDeleteThanks, Cliff. Two things: The people responsible for allocation or curtailment of water have to take increased demand for all uses into account. Water "rights" have been issued for much more water than is usually available. Retaining as much water as possible in any given drainage is wise. Reservoirs are among the most expensive ways, and fraught wit land use and other impact issues. Upland soil, forest and vegetation management are also a good option.
ReplyDeleteCorrection Riverview LLP. Not riverside
ReplyDelete