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3. Climate Change Vulnerability Assessment Drought A drought occurs when conditions are drier than normal for an extended period, making less water available for people and ecosystems. Droughts are a regular occurrence in California; however, scientists expect that climate change will lead to more frequent and more intense droughts statewide. Overall, precipitation levels are expected to remain similar, with more years of extreme precipitation events. East Bay Municipal Utility District (EBMUD) obtains fresh water supplies for San Leandro and other East Bay communities from the Mokelumne River watershed in the Sierra Nevada. Drought conditions can cause smaller streams to run dry, which can subsequently harm the plants and animal habitats within the ecosystem. In an early -century drought (2023 to 2042), the City could experience a drop in average precipitation from an average of 19.0 inches per year to an average of 16.7 inches per year, which would lower baseflows in streams from an average of 4.9 inches per day to 3.7 inches per day.35 In a late -century drought (2051 to 2070), precipitation could also drop to an average of 16.7 inches per year and cause baseflows in streams to drop to 3.6 inches per day.36 Drought conditions could lower water quality and raise water temperatures, reducing dissolved oxygen levels and promoting algae growth that can harm a variety of fish species 37 Wetlands and riparian habitats could experience increased soil erosion, degradation of landscape quality, and loss of biological productivity. Since wetlands act as a buffer between developed areas and San Francisco Bay, helping to protect the community from SLR and bayshore flooding, degradation of wetlands could reduce the amount of water that the ecosystem can absorb and limit the protection that the wetlands provide. Drought conditions can also dry out vegetation, increasing its vulnerability to pests and disease and promoting wildfire conditions. Extreme Heat Extreme heat occurs when temperatures rise significantly above normal levels. In San Leandro, an extreme heat day occurs when temperatures reach above 88.8 degrees Fahrenheit (°F). As shown in Figure 10, the number of extreme heat days in San Leandro 1P projected to increase from 4 days historically, to an average of 12 extreme heat days per year by midcentury and an average of up to 22 extreme heat days per year by the end of the century. Extreme heat can also occur in the form of warmer nights when temperatures do not drop overnight and provide relief from the heat. In San Leandro, a warm night occurs when the temperature remains above 60.9°F.2 As shown in Figure 110, the number of warm nights ilh San Leandro is projected to increase from an average of 4 historically, to an average of 50 2 According to Cal -Adapt, a warm night occurs when daily minimum temperature is higher than 98 percent of the observed daily minimum temperatures between April and October from 1961 to 1990. San Leandro 2021 Climate Action Plan Page 49