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Boulder Hazard Mitigation Plan Introduction Regional Context The southwest is incredibly vulnerable to the impacts from climate change. The region is made up of an assortment of ecosystems ranging from coastal land and deserts to mountains and high elevation forests. Even with a variety of ecosystems, the region is collectively experiencing rapid changes in average temperatures and precipitation variability. Figure 1-2 Change in Temperature in the Southwest N Change in Temperature (7) 0.5 1.0 1.5 2.0 2.5 3.0 Source: NCA 2018 Chapter 25 Group, Oregon State University Figure 1-3 Drought Impacts in the Southwest Source: PRISM Climate I�hp,Pd�>tnA.,..6M�VOM.M. 30 ZD ,>a°° fe°o ,ew 1sm ,eaa °ana mm r..r °` unver cdenenern weecmxn $20 e t°W Jon 19W KPW 116 7°6, 70¢0 V. The climate of the Intermountain West is mimicking trends seen at the global and national scale. Over the past 30 years, the average temperature in the Intermountain West has increased by nearly two degrees Fahrenheit; a rapid pace that is unlike other periods of warming. This region is expected to continue warming. Similar to global and national projections, the Intermountain West is projected to warm by 2 to 6.5 degrees by mid-century (WWA). Local Context Climate models for Colorado show potential for both increased and decreased precipitation, but models are in overall agreement that the hottest recorded summer temperatures in the state will become the new normal; spring snowpack will decrease between 5% and 20%; and streamflows will decrease by up to 30% by 2050 (WWA 2018). In Boulder County, climate data show that the number of 95-degree days has already doubled from 5 to 11 between 2000-2017. Projections indicate that this number will grow to 38 days above 95 degrees by 2050, and 70 days above 95 degrees by the end of the century (Rocky Mountain Climate Organization 2016). Climate change models exhibit a much wider variation in projecting precipitation events, but the models agree that the number of large or heavy storms, with precipitation over 1/2 inch, will increase in both quantity and intensity. Storms creating over 1" of precipitation are likely to increase by 50% by the end of the century (Rocky Mountain Climate Organization 2016). While the mountains will see an increase in large storm events, there will also likely be a reduction in overall precipitation at high elevations, including up to a 5% reduction in precipitation during the summer months by the end of the century (Rocky Mountain Climate Organization 2016). Accompanying the changes in temperature, the number of drought months will nearly double compared to their historic occurrence, and drought events will be classed as "severe" and "extreme" according to the Palmer Drought Severity Index (Resilient Analytics 2018). The combination of increased drought and higher temperatures will further reduce moisture availability within soils, making drought impacts on vegetation more severe and impacting road and infrastructure foundations (Resilient Analytics 2018). Water availability