14 ATTACHMENT 1 EXHIBIT A - Laserfiche WebLink

Chapter 6 Water Supply Characterization THE CITY OF PL£ASANTON • Changes in the timing, intensity, and variability of precipitation, and an increased amount of precipitation falling as rain instead of as snow • Long-term changes in watershed vegetation and increased incidence of wildfires that could affect water quality • Sea level rise and an increase in saltwater intrusion • Increased water temperatures with accompanying potential adverse effects on some fisheries and water quality • Increased evaporation and concomitant increased irrigation need • Changes in urban and agricultural water demand As described above, the SWP has been and will continue to be the largest source of Zone 7's, and hence the City's, water supplies. In 2045, the supplies derived from the SWP (existing SWP supplies, groundwater (stored SWP supplies), and SWP carryover) are projected to represent about 75 percent of Zone 7's supplies. The following summarizes the potential impacts of climate change to water supply operations in the Delta, as they relate to water supply reliability, water quality, and flood control: • Water Supply Reliability The operation of storage reservoirs could be impacted by shifting runoff and snowmelt patterns, requiring a greater volume of flood control storage, and making it more difficult to refill reservoir flood control storage during late spring or early summer, and potentially reducing the volume of surface water available for use during the summer/fall season. Levee breaks, either as a result of the impacts of rising sea levels, lack of maintenance, earthquake, or some combination, could have adverse effects on Delta water quality (due to the intrusion of salt water into these potable water supplies) and water system operations. Major levee breaks could take months or years to repair and will impact the availability of water supplies from the Delta. • Water Quality More intense storms and increased runoff could impact Delta water quality in two ways: 1) Increased sediment load, and 2) Increased contaminants from increased urban and agricultural runoff. Sea level rise could push salt water from the Bay into the Delta, impacting overall water quality and potentially impacting Delta operations. Levee breaks, either as a result of the impacts of climate change or an earthquake, could cause large amounts of salt water from the Bay to enter the Delta and would have adverse effects on Delta water quality and water system operations. The saltwater intrusion could take months to dissipate depending on the severity of the levee break and the magnitude of saltwater intrusion. • Flood Control WEST YOST Reservoir operations, including the need for more flood storage reservoir space, could be impacted by snowpack changes, shifts in snowmelt patterns, and changes in rainfall intensity. 6-33 City of Pleasanton 2020 Urban Water Management Plan May 2021