addressing climate change adaptation in regional transportation plans

Cal-Adapt ProjectionsTable 29. Summary of Cal-Adapt Climate Projections for the North Sierra RegionEffectTemperatureChange,1990-2100PrecipitationHeat WaveSnowpackWildfireRiskRangesJanuary increase in average temperatures: 2.5°F to 4°F by 2050 and 6°F to 7°F by 2100. Thelargest changes are observed in the southern part of the region.July increase in average temperatures: 4°F to 5°F by 2050 and 10°F by the endof the century, with the greatest change in the northern part of the region.(Modeled average temperatures; high emissions scenario)Precipitation decline is projected throughout the region. The amount of decreasevaries from 3 to 5 inches by 2050 and 6 inches to more than 10 inches by 2100,with the larger rainfall reductions projected for the southern portions of the region.(CCSM3 climate model; high carbon emissions scenario)Heat waves are defined as five consecutive days over 83°F to 97°F depending on location. By2050, the number of heat waves per year is expected to increase by two. A dramatic increase inannual heat waves is expected by 2100, eight to 10 more per year.Snowpack levels are projected to decline dramatically in many portions of the region. Insouthern portions of the region, a decline of nearly 15 inches in snowpack levels – a more than60 percent drop – is projected by 2090. (CCSM3climate model; high carbon emissions scenario)Wildfire risk is projected to increase in a range of 1.1 to 10.5 times throughout the region, withthe highest risks expected in the northern and southern parts of the region.(GFDL climate model; high carbon emissions scenario)[Public Interest Energy Research, 2011. Cal-Adapt. Retrieved from http://cal-adapt.org]Water SourcesThe North Sierra climate region primarily overlaps two Department of WaterResources hydrologic regions: Mountain Counties and North Lahontan. The SierraNevada snowpack is the major water source for the entire state of California, butlocal populations rely on local surface and groundwater resources. For example,South Lake Tahoe’s primary water supply comes from underground aquifersthrough wells, and not from Lake Tahoe. Groundwater aquifers are located inareas such as the upper portions of the substantial Feather River watershed(DWR, 2009). Melting of snowpack provides groundwater recharge throughoutthe Sierra Nevada and valley aquifers. Reservoirs with the largest capacities, overone million acre-feet, depend on water derived from the Sierra Nevada andinclude the Don Pedro, Lake Almanor, Lake McClure, New Melones, and Orovillereservoirs (DWR, 2009).Biophysical CharacteristicsThe elevation of the counties in the North Sierra region range from under,1000feet above sea level on the eastern edge of the Central Valley to 14,000 feet abovesea level at some of the higher mountain peaks. Major land forms include thecanyons in the Sierra Nevada carved by glaciers, such as Yosemite Valley.PAGE 74APG: UNDERSTANDING REGIONAL CHARACTERISTICS