Every few years, a shift in the temperature of the Pacific Ocean sets off a chain of atmospheric events that reaches all the way to the Sierra Nevada — changing how much precipitation falls on the Yuba River watershed and in what form. That shift is El Niño, and forecasters are predicting a strong one this winter. For communities that depend on the Yuba’s water, and for the salmon, forests, and meadows that depend on water, an El Niño year raises real questions: How much water is coming? Will it fall as snow or rain? And what does it mean for a watershed already navigating the compounding pressures of climate change?  

 El Niño is part of a natural cycle called the El Niño-Southern Oscillation, or ENSO. ENSO has two phases, the cooler phase known as La Niña, and the warmer phase known as El Niño – so named because South American fishermen in the 1600s noticed the warmer-than-normal coastal waters around Christmas time which had a negative impact on fishing. This year that warm water is showing up early, and is extra warm. 

To understand what El Niño means for the Yuba, it’s important that we first understand how warmer-than-normal sea surface temperatures near the equator impact weather here. Warm equatorial air holds lots of water in it; we experience this as humidity in the tropics. But warm air also rises. As it rises, it cools, leading to clouds and ultimately rain. When equatorial water off the coast of South America is extra warm, it means this process is supercharged with higher temperatures and more water vapor (think higher humidity) available in the atmosphere to form clouds and, ultimately, precipitation.  

As this air rises and cools, it also moves north, which further contributes to its cooling. Because Earth is spinning, and that rotation is at an angle, we see three general areas, or cells, of rising and cooling air known as the Hadley cell, Ferrel cell, and Polar cell.

During the El Niño phase of the ENSO cycle, the Hadley cell (#1 in the figure) becomes more vigorous, meaning more warm wet air is flowing north. When this extra wet air meets the jet stream, which carries cold air from high latitudes, it results in above-average storms across the southern portion of the US. Where those two processes, the Hadley cell and Jet Stream, meet will determine what this El Niño will mean for the Yuba. 

It is impossible to know with certainty what this El Niño year will mean for the Yuba. More water falling from the sky is highly likely, but whether that water falls as rain or snow, and at what elevation the line between rain and snow occurs will be impossible to predict. We can’t know for sure if the snowpack this year is going to be large or plagued by high elevation rain (for what it’s worth, my family got season passes though). 

One thing we do know is that as global climate change makes precipitation events more extreme, adding an El Niño cycle on top of that means having accurate storm forecasting is crucial. Much of the largest flooding in recent memory has occurred as a result of rain-on-snow events during El Niño years. El Niño years can mean deep snowpacks or high elevation rain. The more accurate the storm forecasting water managers have, the better able they are to manage water infrastructure to respond to the falling water. The difference between needing to release water early to make way for the deluge of a rain-on-snow event or not can be a matter of a few degrees in temperature or hundreds of feet in elevation. The advanced forecast models at NCAR and NOAA (that you advocated for) will be crucial for water managers this winter.  

Across the watershed, SYRCL’s meadow, forest, and lower Yuba restoration work is built to weather whatever storms we may get. At its core, our restoration work is designed to restore natural processes. Frequently, that means slowing water down and spreading water out. So, even if the high elevations see increased rainfall due to El Niño, that water is more likely to become groundwater and less likely to runoff the landscape (which triggers erosion and could lead to flooding). Likewise, reconnecting floodplains in the lower Yuba not only creates additional safe habitat for juvenile salmon to rear, it also decreases flood crests downstream and helps recharge groundwater. 

Every acre of meadow restored, every floodplain reconnected, every forest treated to reduce runoff is an investment in a watershed that can weather whatever comes: an El Niño winter, a drought year, and the increasingly unpredictable conditions that climate change continues to deliver. 

The work is ongoing, and it depends on a community that understands why it matters and chooses to support it. If this winter’s forecast tells us anything, it is that the time to invest in a resilient Yuba River watershed is before the storms arrive. Support SYRCL’s restoration work today and help ensure that whatever this El Niño brings, the Yuba River watershed is ready for it.