2020 Local Hazard Mitigation Plan

City of Irvine

has taken significant steps towards reducing water supply scarcity during a drought, the City may not feel the effects of drought in the same way other cities in southern California may. Approximately 65 percent of the City’s water is sourced from groundwater from Orange County Water District. To supplement this water supply, IRWD also uses imported water from ‘MWD, which is sourced outside of southern California. The location of this water could be subject to a long-distance drought — a drought that occurs when a distant water source becomes less av ailable. Given that most of Irvine’s water comes from local groundwater sources, however, this type of event would have to be exceptional or prolonged for the City and its residents to feel the impact. The U.S. Drought Monitor Classification Scheme is a common scale used to measure the impact of droughts in different communities across the United States. Table 3-9 describes the category, description, and possible impacts associated with a drought event.

Past Events

Irvine, like the rest of California, has experienced many drought events throughout its history. Each event has been distinct, with varying lengths, severity, and frequency. One of the earliest recorded major droughts in state history is known as the “Great Drought , ” which occurred in 1863 and 1864. This drought killed 46 percent of the cattle in the state and ultimately led to the decline of cattle ranching in the state. 59 The “Dustbowl Droughts, ” l asting from 1928 to 1935, caused great impacts to the state’s agriculture. The effects of this drought were so severe that it sparked the movement to create some of California’s modern water irrigation infrastructure, such as the California Aqueduct. Another

Shasta Lake Reservoir seen during the 1976-1977 drought. Image from Steve Fontanini.

drought occurred in 1976 and 1977, which lead to agricultural losses estimated at nearly $1 billion. This drought lead to water-saving practices that are still in effect today across the state. Further water conservation practices were enacted during a drought lasting from 1987 to 1993, which caused agricultural damages at an estimated $250 million each year. 60

Table 3-9: U.S. Drought Monitor Classification Scheme 61