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Reviews |  California drought is worse than we thought


Outside my lab near Donner Pass in California’s Sierra Nevada Mountains, new animal tracks are on the snow after a winter of hibernation, birdsongs soar through the air and the creek flows strongly with water from melting snow. Spring arrived very early in the Sierra Nevada.

Last week, I joined teams of other scientists gathering the most important measurements of the Sierra Nevada snowpack from more than 265 sites across the state. Typically, this measurement marks the transition from the snow accumulation season to the melt season and contains the most snowfall of any measurement throughout the year. The 2022 results, however, confirmed what those of us monitoring the state’s drought had feared: California’s snowpack is now at 39% of its average, 23% less than in the past. same time last year. This signals a worsening drought – already the worst in the western United States in 1,200 years – and another potentially catastrophic fire season for much of the West.

Many people have a rather simplistic view of drought as a lack of rain and snow. That’s right – to some extent. What it does not take into account is human activity and climate change which are now dramatically affecting available water and its management. As more frequent and larger wildfires and extended dry spells hit the land, our most important tools for managing water are becoming less and less precise. At the same time, our reliance on these models to try to make the most of the little water we have is becoming increasingly problematic.

Droughts can last several years or even more than a decade, with varying degrees of severity. During these types of prolonged droughts, the soil can become so dry that it absorbs any new water, reducing runoff to streams and reservoirs. The ground can also become so dry that the surface becomes hard and repels water, which can cause rainwater to run off quickly and cause flooding. This means that we can no longer rely on relatively short periods of rain or snow to fully relieve drought conditions as we have with past droughts.

Many storms with near-record amounts of rain or snowfall would be needed in a single year to make a significant breach in drought conditions. October was the second snowiest month and December was the snowiest month on record at the Snow Lab since 1970 thanks to two atmospheric rivers hitting California. But exceptionally dry spells from November and January through March left us with another year of below average snow, rain and runoff.

This type of feast or famine winter with big storms and long, severe dry spells is expected to increase as climate change continues. As a result, we will need several years of above average rain and snow to make up the difference rather than consecutive major events in a single year.

Even with years of normal or above-average precipitation, land surface changes present another complication. Massive wildfires, such as those we’ve seen in the Sierra Nevada and Rocky Mountains in recent years, are causing distinct changes in how snow melts and how water, including rain, drains from the countryside. Loss of forest canopy due to fires can lead to higher wind speeds and temperatures, which increase evaporation and decrease the amount of snow water reaching reservoirs.

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Similar to prolonged drought, fire also changes soil properties and can create flash floods during periods of heavy rain. These landscape changes, feast-or-famine rainfall patterns, and increased demand for water supplies make water management in the West a precarious and difficult task.

One of the most important tools for managing water during times of drought are the models developed by various state and federal agencies such as the National Weather Service’s Office of Hydrologic Development, the Army Corps of Engineers, and California Department of Water Resources. Yet these models suffer from the same simplistic view of drought and water, and they urgently need updating.

Land surfaces, snowmelt patterns, and climate have all changed since many of these models were developed, which means they are missing crucial pieces of today’s water puzzle. What has held back model updates for decades is dwindling funding for science and engineering.

Models may not be able to reliably tell water managers how much rain and snow will run off land into reservoirs, which can mean severe shortages in the worst case. Given dwindling reservoir levels and meager snowfalls in recent years, the discrepancies between water expected and arriving could be the difference between having water in the taps or entire towns slumping. dry up.

We look at the barrel of a gun loaded with our water resources in the West. Rather than investing in bulletproof vests, we were hoping the trigger wouldn’t be pulled. Current water monitoring and modeling strategies are not sufficient to support the growing number of people who need water. I worry about the week, the month, the year ahead and the new problems we will inevitably face as climate change continues and water becomes more unpredictable.

It is time for decision makers who allocate funds to invest in updating our water models rather than maintaining the status quo and hoping for the best. Large-scale investment in the agencies that maintain and develop these models is essential to prepare for the future of water in the West.

Better water patterns ultimately mean more precise water management, which will lead to greater water security and availability for the millions of people who now depend on the changing supply. in water. It is an investment in our future and, moreover, an investment in our continued ability to inhabit the water-scarce regions of the West. It’s the only way to make sure we’re ready when the trigger is pulled.

Dr. Schwartz is the Principal Scientist and Station Director at the University of California, Berkeley, Central Sierra Snow Lab.

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