Outside my lab near Donner Pass in the California Sierra Nevada, there are new animal footprints in the snow after a hibernating winter, the birdsong rises through the air and the stream flows strongly with the water of the melting snow. Spring has arrived in the Sierra Nevada in a worrying way.
Last week, I joined teams of other scientists who put together the most important measurements of the Sierra Nevada snow cover from more than 265 locations across the state. Typically, this measure marks the transition from the snow accumulation season to the melting season and contains the largest amount of snow of any measure throughout the year. The 2022 results, however, confirmed what we feared as we watched the state’s drought: California’s snow cover is now at 39 percent of its average, or 23 percent lower than at the same point last year. This indicates a deepening drought, which is 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 the lack of rain and snow. This is accurate, 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 large forest fires and prolonged dry periods plague the land, our most important tools for managing water are becoming less and less accurate. At the same time, our confidence in these models to try to make the most of the little water we have is becoming increasingly problematic.
Droughts can last for 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 all the new water, which reduces runoff into streams and reservoirs. Soil can also become so dry that the surface becomes hard and water-repellent, which can cause rainwater to spill quickly from the ground and cause flooding. This means that we can no longer rely on relatively short periods of rain or snow to completely alleviate drought conditions as we did with previous droughts.
Many storms with near-record amounts of rain or snow would be needed in a single year to make a significant impact in drought conditions. October was the second snowiest month and December the snowiest month recorded in the snow lab since 1970, thanks to two atmospheric rivers that hit California. But the exceptionally dry periods of November and January to March have left us with another year with below average snow, rain and runoff conditions.
This type of holiday or famine winter with severe storms and long, intense dry periods is expected to increase as climate change continues. As a result, we will need several years of rain and snow above average to make up for the difference instead of large consecutive events in a single year.
Even with normal or above-average rainfall years, changes in the earth’s surface present another complication. Massive wildfires, such as those we have seen in the Sierra Nevada and the Rocky Mountains in recent years, cause different changes in the way snow melts and water, including rain, runs out of the landscape. Loss of forest cover due to fires can lead to higher wind speeds and temperatures, which increase evaporation and decrease the amount of snow water that reaches the reservoirs.
The climate, and the world, are changing. What challenges will the future bring us, and how should we respond?
Similar to prolonged drought, fire also alters soil properties and can create sudden flooding during periods of heavy rainfall. These changes in the landscape, the precipitation patterns of partying or starvation, and the increasing demand for water supply make water management in the West a precarious and difficult task.
One of the most important tools for managing water during periods of drought are the models developed by various state and federal agencies such as the Office of Hydrological Development of the National Meteorological Service, the Army Corps of Engineers and the Department of California Water Resources. However, these models suffer from the same simplistic view of drought and water, and need urgent updating.
Land surfaces, snowmelt patterns, and climate have changed since many of these models were developed, which means that crucial pieces of the current water puzzle are missing. What has prevented model upgrades for decades is the reduction in funding for science and engineering.
Models may not be able to reliably tell water managers how much rain and snow will escape from land to reservoirs, which can mean severe shortages at worst. Given the reduction in reservoir levels and the meager mantles of snow in recent years, discrepancies between the amount of water expected and the amount of water that could arrive could mean the difference between having water on taps and dry whole villages.
We are looking down the barrel of a gun loaded with our water resources in the West. Instead of investing in body armor, we have hoped that the trigger will not be taken. Current water monitoring and modeling strategies are not enough to support the growing number of people who need water. I am concerned about the coming week, month and year and the new challenges we will inevitably face as climate change continues and water becomes more unpredictable.
It is time for policy makers to invest in updating our water models instead of maintaining the status quo and waiting for the best. Large-scale investment in the agencies that maintain and develop these models is critical to preparing for the future of water in the West.
The best water models ultimately require more careful water management, and this will lead to greater water security and availability for the millions of people who now depend on changing water supply. It is an investment in our future and, in addition, an investment in our continued ability to inhabit the water-scarce western regions. It’s the only way to make sure we’re ready when we pull the trigger.
Dr. Schwartz is the Chief Scientist and Director of the University of California, Berkeley Station, Central Sierra Snow Lab.
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