Digging into the snowpack as of March
The news could be better.
Hello, and welcome to a (snow)packed edition of Western Water Notes.
Snowpack is one of the most important indicators of water supply in the West. As snow melts, it recharges ecosystems and replenishes reservoirs that provide drinking water for millions of people and irrigation water for millions of acres of farmland.
How much snow falls—in addition to where and when—is something water managers watch closely. And this year, the tl;dr version is that snowpack is average or a little less than average in most places. But the details matter a great deal, and things are highly dependent on where exactly in the West you are.
See below a map from the USDA’s National Resources Conservation Service that shows how snowpack is distributed in basins across the Western U.S.
In the Northwest, things generally look better, but in the Southwest, the accumulation of snowpack, as a percent of the 1991-2020 median, does not look as good.
To be more specific, in Arizona and New Mexico, it is “abysmal.” Don’t just take my word for it, either. That’s how the National Integrated Drought Information System (NIDIS) described it in their narrative summary this morning.
New Mexico environmental writer Laura Paskus reported some more narrative from local hydrologist Karl Wetlaufer on the record-low snow levels:
February brought another month of well below median precipitation across the entire Rio Grande basin. As one would anticipate this generally led to lowered forecast volumes over a month ago. It is worth noting that similar to last month there remains a broad gap between current percent of median snowpack and water year precipitation. This is a result of a wet October and early November followed by several months of dry conditions. These persistent dry conditions have led to record lowest or otherwise very low rankings of snowpack compared to the period of record for March 1st.
Here are some more key points from the NIDIS report:
Another month of extremely dry conditions plagued the Southwest (Colorado, New Mexico, Arizona, Utah, Nevada), leading to deepening snow deficits across already dry basins. Exceptional snow drought continues to persist with the peak snow water equivalent (SWE) dates past for Arizona and New Mexico.
Lower-elevation snow drought persisted across southern Alaska due to continued warm and dry conditions, with Anchorage Airport recording its driest February on record. Large areas in southwest Alaska and low elevations in south-central Alaska—which are typically snow covered—were (nearly) snow-free as of March 1.
Moderate snow drought conditions persisted in the northern and central Cascade Range of Washington due to below-average winter precipitation.
A recent storm cycle brought welcome moisture back to California and Nevada, improving snow drought conditions, but deficits still remain in the region.
The Upper San Juan, Upper Rio Grande, and Gunnison River Basins provide substantial snowmelt and runoff to the Upper Colorado River Basin, which drains into Lake Powell. Given low snowpack in these basins, monitoring snow conditions will be critical for future water supply as the basins enter the spring snowmelt season.
The National Weather Service Climate Prediction Center’s outlooks favor a likely colder and wetter pattern over the next month in the West, which could be favorable for snow accumulation.
As the summary notes, conditions have improved in California and Nevada, especially in northern Sierra mountain ranges. February helped to boost snow levels after a dry January. I found this chart (showing monthly precipitation as a percent of median) in the Nevada Water Supply Outlook especially notable because it’s a clear display of the stark difference between snow in January and February was.
But central and southern Sierra Nevada basins are still lagging behind the average at around 85%. Over the weekend, I spent some time near Donner Pass outside of Lake Tahoe, and it was remarkable though not surprising to see how little snow was on the ground at low elevations after warm storms in February.
A lot of precipitation at lower elevations has fallen not as snow but as rain, consistent with the type of snowpack retreat that is forecast as the climate changes. The L.A. Times noted this trend in a story I linked to earlier this week.
The snowpack alone is not the only thing water managers are watching.
A key question is how much snow will actually make it into rivers as streamflow. The answer hinges on a number of factors, including soil moisture. Wet soils could blunt the impact that poor snowpack has on overall drought. Wet soils would make runoff more efficient. But the opposite is also true.
In this regard, the Colorado River Basin—where state negotiators are locked in tense talks about future allocations in the watershed—is a place to watch, as it has been in the past. Several sub-basins within the Colorado River watershed lag below normals, though in total, the Upper Colorado River basin sits at about 90% of average. Still, as the NIDIS report notes, federal water managers forecast streamflow to be at about 70% of normal—in part because of soil moisture.
So where does that leave us?
In the southern part of the Western U.S., the probability of reaching an average year is not looking good, according to an analysis from the Center for Western Weather and Water Extremes. Here is how the California Department of Water Resources put it:
While forecasts show storm activity may pick up in March, there is no guarantee it will be enough for the snowpack to catch back up to average by April 1. California has seen several years in recent history with large early season snow totals, only for predominantly dry conditions to dominate the rest of the season.
Still, everyone hopes for a Miracle March. More could happen in the next few weeks, especially with some colder weather is in the forecast. ❄️
Some other stories:
There’s a lot going on right now, and a lot of news to keep track of. I’ll be back with more next week. But until then, here are some links to help stay informed.
Over at the Land Desk, Jonathan Thompson wrote about how DOGE could result in the Department of Interior—and its offices—withdrawing from the West.
Relatedly, there’s been a lot of important reporting on DOGE targeting offices belonging to the Bureau of Reclamation and cuts to an agency responsible for keeping dams and diversions operating across the West.
In response to cuts at the bureau, POLITICO reported on water agencies sending a letter to the Trump administration’s Interior Secretary.
This week, the U.S. Supreme Court issued a 5-4 ruling in favor of San Francisco’s challenge to a Clean Water Act permit. In court, the city’s claims were supported by the National Mining Association and others. The ruling has potentially broad implications beyond San Francisco, and in practice, could make it harder for the agency to enforce the Clean Water Act. More to come on that.
Goes without saying that the mention of domestic critical minerals caught my attention on Tuesday night. More on that here. Big implications for Nevada.
From the Public Policy Institute of California: How three (fairly) wet winters could help California’s salmon.
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