Snowpack Levels Up Over 250%: Severe Flood Risk?
Edited March 15th, 2023 by Kyle Langan
In December 2021, Conrey published an article about Sierra storm systems and the benefit to California’s then struggling mountain snowpack. Without these storms, a resulting decrease in the extent of alpine tundra ecosystems could have threatened wildlife.
At the start of February 2022, we revisited this prediction when the Sierra snowpack ballooned to more than double its usual size for that time of year.
Another month and a half later, and the Sierras are now seeing a “historic run of atmospheric rivers and punishing arctic blasts that have filled reservoirs, flooded cities and eased drought conditions across California” (Rodgers, 2023). With two weeks still left in March, the South Sierra Snow Water Content currently sits at 260% of average for April 1st, according to California Department of Water Resources (California Snow Water Content, 2023). In Southern Nevada, the Spring Mountains saw numbers as high as 410% over today’s median:
Check updated California / Nevada snowpack levels HERE.
As seen in the chart above, the snow water content previously hit its record size during the winter of 1982-83, as tracked by the green trend lines; 2022-23’s current blue trend lines show relief for California’s multiyear drought (California Snow Water Content, 2023). As of March 11th, “52 feet of snow had fallen at the UC Berkeley Central Sierra Snow Lab atop Donner Summit, tying the 1981-1982 season for the fourth-highest total since the lab was created in 1946, said Andrew Schwartz, lab manager and lead scientist. Schwartz expects this season to end up second only to the 1951-1952 winter season when nearly 68 feet of snow fell” (Rodgers, 2023).
Rain-on-Snow Events: Property Exposure
The flood risk is difficult to forecast, but property owners should prepare for atmospheric rivers. “Atmospheric rivers form when a long channel of wind transports water vapor from the tropics, and they produce heavy rain or snow when they make landfall” (Rodgers, 2023). Rain on top of snowpack could bring “rain-on-snow events, when runoff from rain combines with snowmelt to overwhelm watersheds” (Lee, 2023). For example, Kern River normally “runs at 600 cubic feet per second. During a ‘great’ summer river flow, it is around 7,000 cubic feet per second. In the climax of the storm on Friday, March 10th, the river was running at 45,000 cubic feet per second” (Garcia, 2023). Later this spring, uncertainty rises. The risk depends on whether the snowpack melts gradually or rapidly. A series of warm storms later in the spring will elevate property risk due to flooding (Lee, 2023). Property owners do not want a spring heatwave, which leads to more rain-on-snow and potential flooding or mudslides.
References
California Snow Water Content, March 14, 2023, percent of April 1 average. (n.d.). Retrieved March 14, 2023, from https://cdec.water.ca.gov/reportapp/javareports?name=PLOT_SWC
Flores, J., & Lee, J. (2023, March 11). Map: These are the areas facing serious flood risks in California storm. San Francisco Chronicle. Retrieved March 14, 2023, from https://www.sfchronicle.com/weather/article/map-shows-flood-risk-17830177.php
Garcia, L. (2023, March 13). Kern River once again flowing through Bakersfield after Weekend Rain. KGET 17. Retrieved March 14, 2023, from https://www.kget.com/news/local-news/kern-river-once-again-flowing-through-bakersfield-after-weekend-rain/
Lee, J. (2023, March 13). ‘whole hell of a lot of water up there’: This map shows the sierra snowpack’s record levels. San Francisco Chronicle. Retrieved March 14, 2023, from https://www.sfchronicle.com/weather/article/california-snowpack-record-17836514.php
Natural Resources Conservation Service. California/Nevada SNOTEL Snowpack Update Report. (n.d.). Retrieved March 14, 2023, from https://wcc.sc.egov.usda.gov/reports/UpdateReport.html?report=California%2FNevada&format=SNOTEL%2BSnowpack%2BUpdate%2BReport
Radde, K. (2023, March 13). A waterlogged California is bracing for yet another Atmospheric River. NPR. Retrieved March 14, 2023, from https://www.npr.org/2023/03/12/1162936998/a-waterlogged-california-is-bracing-for-yet-another-atmospheric-river#:~:text=Atmospheric%20rivers%20form%20when%20a,snow%20when%20they%20make%20landfall.
Rodgers, J. (2023, March 12). 52 feet and counting: Lake Tahoe grapples with ‘ginormous’ snowpack. Stars and Stripes. Retrieved March 14, 2023, from https://www.stripes.com/theaters/us/2023-03-12/california-storms-lake-tahoe-snowpack-9470968.html