While overall hydro generation in the Pacific Northwest has been mostly stable so far this month—thanks in part to the ongoing chum spawning operation, that supports Lower Columbia flows to maintain the river level above 11.3 feet on the Bonneville tailwater from early November through close to the end of December, using stored water from behind Grand Coulee to augment flows if necessary—that is not to say that the Northwest has seen no changes in hydro-relevant conditions.  After a fairly wet start to November, things have dried up significantly in recent days.  While this is not having much of an impact on current flows or generation, it could have implications for later in the water year. 

Figure 1 | NWRFC ESP10 Jan-Jul Water Supply Forecast for The Dalles 

The month of November in recent years has been a period of significant change when it comes to the water supply forecast for the heart of the water year.  The figure above focuses on the January through July seasonal period, plotting the Northwest River Forecast Center’s ESP10 water supply forecast for Jan-Jul total runoff volume through The Dalles.  The daily forecast for the current water year is shown, as are those of the previous three years.  Notably, each year shows a sharp decline in forecasted water starting at the beginning of November and continuing throughout the month and into December.  This November has followed the same pattern.  After entering the month of November with a forecast number of 97 MAF (which would be 93% of normal, compared to the actual end-of-season numbers sitting between 76-79% of normal the past three years), the decline over the first 18 days of the month brought the forecast to a low of 87.8 MAF on Tuesday, stepping up to 88.7 MAF yesterday (85% of normal).  Unregulated flows for the season is the number one driver of generation within the hydro system over the course of the water year.  The recent decline is bad news for those of us hoping for 2026 to break the pattern of three very dry years in a row (and 4 of the past 5). 

Figure 2 | Daily Total Snow Water Equivalent 

We can see how the change has been reflected in the early snow accumulation within the PNW as well.  In late October and early November, snow water equivalent (shown in the figure above) was building up faster than is typical in the Columbia basin and was right on track with the average for the Snake.  But since the end of the first week of the month, snow pack has leveled off—and even declined for the Columbia as some warming in the weather led to some melt off.  As is clear from the figure, there is still a long way to go to make up for lost ground but it looks like the Northwest is getting off to a poor start this winter.

At Energy GPS, we want to help keep you informed and empowered to stay up to date with the ever-changing hydro landscape.  As part of our Enterprise power packages we offer the latest news and analysis in all thing PNW hydro.  Reach out to us at [email protected] for more information. 

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