Climate and Energy Action Plan (CEAP)

CLIMATE TRENDS & PRO JECTIONS | CITY OF ASHLAND, OREGON | FINAL REPORT | 25 Table 4. SNOTEL (ST) and Snow Course (SC) stations with data beginning at least by 1960 in the Rogue Basin ordered greatest to least percent decline . An asterisk denotes a statistically significant trend at the 95% level . Station Name Elevation (Feet) % Change Trend (cm/yr) MeanSWE (inches) DeadwoodJunction_SC 4660 -60.0 -0.2 5.2 DiamondL ake_ST 5280 -58.5 -0.6* 15.1 HowardPrairie_SC 4580 -38.9 -0.1 5.7 FishLk._ST 4660 -32.9 -0.2 8.9 FourmileLake_ST 5970 -31.2 -0.5 28.7 BillieCreekDivide_ST 5280 -25.4 -0.3 21.0 SilverBurn_SC 3680 -20.4 -0.1 8.9 BeaverDamCreek_SC 5120 -20.3 -0.1 10.1 AnnieSprings_ST 6010 -19.7 -0.4 41.8 ColdSpringsCamp_ST 5940 -7.1 -0.1 27.2 ParkH.q.Rev_SC 6570 -5.1 -0.1 58.7 BigRedMountain_ST 6050 -2.6 0.0 27.4 SiskiyouSummit_SC 4560 100.8 0.1 4.0 Future Projections Basins in the Pacific Northwest have been class ified into three categories based on the ratio of spring snow water equivalent to wet season (October -March) precipitation (see Figure 17) (Hamlet et al., 2013) . Rain - dominant watersheds , like the Middle and Lower Rogue sub -basins, receive most of their precipitation as rainfall during the winter months and thus have streamflow peaks in winter and low flows in summer. Mixed rain-snow watersheds , like the Upper Rogue sub -basin, tend to have mean temperatures near freezing and therefore receive both rain and snow ; this produces a hydrograph with two peak flows, one in winter and one in late spring associated with spring snowmelt. Snow -dominant watershe ds receive most of their precipitation as snowfall and thus have their peak streamflow during the lat e spring (Raymondi et al., 2013) . As temperatures warm in the future, precipitation is more likely to fall as rain than as snow, particularly at elevations in which winter temperature s hover near freezing. This will reduce the water su pply stored in mountain snowpack (Raymondi et al., 2013) . Widespread declines in April 1 SWE are projected throughout the Columbia River Basin under future clim ate change (Hamlet et al., 2013) . Averaged over the Middle Rogue sub -basin, April 1 SWE is p rojected to decrease by 86% for the multi -model mean by the 2080s under the high emissions scenario compared to the historical baseline (1950 -2005) ( see Figure 18). The range across all models and both emissions scenarios of futur e changes in SWE is -41% to -83% for the 2050s and -58% to -93% for the 2080s ( refer back to Table 2). Across the Pacific Northwest, some of the highest elevation snow -dominant watersheds are likely to remain, but many are likely to trend gradually toward mixed rain -snow watersheds characteristics ( see Figure 17). Mixed rain -snow watersheds are likely to trend gradually toward rain -dominant watershed characteristics including earlier spring melt, reduced s pring peak flows, increased winter flows, and reduced summer flows (Raymondi et a l., 2013) . Averaged over the Middle Rogue sub -basin, m onthly total runoff is projected to shift toward earlier spring melt, higher winter flows, and lower summer flows (see Figure 19).