Even with some winter precipitation – including rain and snow – the West is still at risk for drought, according to a new study published by the Healthy Green Spaces Coalition.
The study looks at six years of data, from 2021 to 2026, to analyze both snow drought and warm rain events. A snow drought is defined as “snow water equivalent (SWE) at or below the 20th percentile, which is a baseline guided by partner expertise and research.” SWE is the amount of water stored within snow.
Warm rain events are exactly what they sound like. When winter precipitation falls as rain instead of snow, that water isn’t stored in the snowpack for eventual later release during the melting and runoff season.
The study’s authors point out that “You can have lots of winter precipitation, yet still end up with a higher drought risk later in the year, because the water never stays stored as snow.”
In particular, warm rain events can cause problems with some reservoirs needing to release water during the winter, because the rain means they won’t have room for projected runoff. That also creates another problem where inflows to that reservoir drop precipitously in the summer, and the inflows can’t meet the outflow demand.
Snow Drought, Warm Rain Increase
This report found that snow drought days were recorded at 37.6% of measuring stations throughout the West. This means that 37.6% of snow measuring stations recorded days of snowpack that were “unusually low” for that time of year, based on the station’s historic averages.
Warm rain events have also increased since 2021, as stations are reporting about 5% more warm rain events on average than in 2021. A warm rain storm drops water, but it’s not stored as snow at that measuring location.
Even with some winter precipitation, how that water falls matters nearly as much as how much arrives. If it can’t be stored and released on a natural timetable, it will impact the entire landscape.
The Angling Takeaway
For anglers, this means streamflows will peak earlier in the season in 2026, and decline sooner. That will likely mean warm river temperatures, probably too warm for ethical trout fishing (when temps rise above the 68-70 degree threshold) sooner than usual, as well.
Rebuilding reservoir levels and recharging groundwater will require another outlier winter in the future.