California’s Lake Oroville, Central Valley Photo credit: The Mercury News
by Dick Hall-Sizemore
Some commenters on this blog have downplayed the effects of climate change and even derided early projections of serious consequences. Except for more frequent flooding in parts of Hampton Roads (which is serious for those directly affected), Virginians have not experienced serious consequences of climate change. However, the American West is experiencing serious effects of climate change and the ramifications of those effects will soon be felt by Virginians, if only indirectly.
Climate change is affecting the resource that has been at the heart of politics and development in the American West since Americans began settling there: water.
States in the American Southwest depend on water from the Colorado River to grow their crops and sustain their towns and cities. Rather, they depend on Colorado River water stored in two huge reservoirs, Lake Powell and Lake Mead. Water from those reservoirs is allocated by law and interstate compacts among the states (and Mexico). Even Southern California has a straw in the Colorado River. The federal Bureau of Reclamation is charged with administering all the agreements.
A recent Wall Street Journal article highlights the decreased flow of the Colorado and the lowering of the levels in the reservoir, with a focus on Arizona. Last year, the federal government declared the first-ever shortage on the Colorado. That declaration triggered an 18% decrease in Arizona’s allocation, which will be implemented this year. On a local level, one county stands to lose all of its allocation next year. It is projected that about half of the farmland in Arizona will remain unplanted this year. If Lake Mead’s water level continues to fall, California’s allocation could be reduced.
The authors of a study published last month report that Southwestern North America is in a “megadrought.” (A megadrought is one that lasts for more than one decade.) It is true that droughts, even long-lasting ones, have occurred throughout history in the Southwest. In fact, using soil moisture as a measure of drought and tree ring history to estimate levels of soil moisture in the past, the authors identify several megadroughts throughout history, going back to the year 800. Based on this research, they conclude that the years 2000-2021 “ranks as the driest 22-yr period since at least 800 c.e.” The second driest megadrought occurred between 1571-1592.
In addition to being the driest, the current megadrought has two major distinctions from earlier megadroughts:
- The others did not occur when millions of people were living in the area.
- The current megadrought is the result of “anthropogenic climate change (ACC)”.
The authors developed a model in which they compared observed soil moisture measurements since 1901 to projected soil moisture levels “simulated under a counterfactual climate without post-1901 ACC trends in temperature, humidity and precipitation.” After stripping out the effects of man-made climate change, they concluded that climate change accounted for more than 40% of the reduction in soil moisture from 2000-2021 (the current megadrought). Their conclusion: “Without ACC, 2000–2021 would not even be classified as a single extended drought event.”
California is also experiencing drought conditions, but the circumstances are different than those in Arizona, and the effects will be felt by Virginians.
There is a caricature of California that involves Hollywood, crowded cities, massive traffic jams, and, at least on BR, a population of wacky progressives. There is likely some truth to this caricature, but California is also a large agricultural state. In fact, it accounts for a greater percentage (over 13%) of the nation’s agricultural revenues than any other state. It is “America’s garden,” producing over a third of the country’s vegetables, including two-thirds of the country’s fruit and nuts.
The state’s main agricultural region is the Central Valley. To provide water for the crops grown there, the region depends on a complex system of dams, reservoirs and canals. Much of the water for that system comes from runoff from the snowpack in the Sierra Nevada Mountains. In fact, the snowpack accounts for about 30% of the state’s water supply.
Another recent Wall Street Journal article has reported on the current dire water conditions facing California this year. Although the state has been struggling through a drought in recent years, there was hope late last year when it experienced one of the wettest Decembers on record. Snow piled up in the Sierra Nevada to depths of more than 15 feet, 154% more than normal. However, January and February were the driest on record. With the lack of precipitation and warmer temperatures, the snowpack on March 1 was only 63% of normal depth. The major reservoirs in the Central Valley were at less than 50% capacity. In February, the federal Bureau of Reclamation informed many farmers in the Central Valley that their water allocation would initially be 0%. As a result, fewer crops will be planted. (Another effect of the ongoing drought was the shutting down of the hydroelectric plant on Lake Oroville last summer because there was not enough water in the lake to spin the blades of the turbines.)
Climate change is a major factor behind the drought in California. For reasons beyond my understanding, studies and observations have shown that climate change will affect the pattern of rainfall. There will be more rain in winter and less in spring and fall, with the start of the spring rains being delayed by up to a month. As for the increased winter rains, higher temperatures mean that less of the precipitation will be in the form of snow.
A recent study confirms that temperature changes have resulted in smaller snowpacks in California. The authors compiled a record of snowpack measurements over time, then modeled that data by removing long-term trends… at each grid point from the model input temperature data (“no-warming”).” The result was that “many areas with large negative trends … switch to smaller negative or even positive trends.” Their conclusion was that “warming is implicated in the large negative trends in [the snowpack] in the Pacific states.”
The authors of the study summarized their findings and the policy implications, as follows:
The magnitude of these changes relative to the built storage (reservoirs), and the certainty with which continued warming will lead to continued declines at a similar or increasing rate, illustrates the immense challenge facing western water managers. Patterns of water use that became established (even entrenched) during the climate of the past cannot be changed without intense political effort owing to large cultural, economic, and infrastructure investments in the status quo ante. Solutions cannot consist solely of future infrastructure: new reservoirs cannot be built fast enough to offset the loss of snow storage, so solutions will have to lie primarily in the linked arenas of water policy (including reservoir operating policies) and demand management.
Therefore, due to smaller snowpacks in the Sierra Nevada Mountains, resulting from climate change, a head of lettuce, a couple of lemons, or a bag of California oranges will cost Virginians more this year and in the foreseeable future.
