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<br /> <br />Drought <br /> <br />1987 to 1992 Drought <br />California received precipitation well below average levels for four consecutive years. While the Central Coast <br />was most affected, the Sierra Nevada range in Northern California and the Central Valley counties were also <br />affected. During this drought, only 56 percent of average runoff for the Sacramento Valley was received. In 1991, <br />the State Water Project sharply decreased deliveries to water suppliers. By February 1991, all 58 counties in <br />California were experiencing drought. Urban areas as well as agricultural areas were impacted. <br /> <br />1976 to 1977 Drought <br />California had a severe drought due to lack of rainfall during the winters of 1976 and 1977. 1977 was the driest <br />period on record in California at that time, with the previous winter recorded as the fourth driest in California’s <br />hydrological history at that time. The cumulative impact led to widespread water shortages and severe water <br />conservation measures statewide. Only 37 percent of average Sacramento Valley runoff was received, with just <br />6.6 million acre-feet recorded. Over $2.6 billion in crop damage was recorded in 31 counties. FEMA declared a <br />drought emergency (Declaration 3023-EM) on January 20, 1977, for 58 California counties. <br /> <br />9.2.3 Location <br />Drought is a regional phenomenon that has the potential to impact the entire planning area. A drought affects all <br />aspects of the environment and the community simultaneously and has the potential to impact every person in the <br />planning area directly or indirectly, as well as adversely affecting the local economy. <br /> <br />9.2.4 Frequency <br />Drought has a high probability in the planning area: <br /> From 2000 through May 2021, some part of San Mateo County experienced a USDM rating of D1 or <br />higher in 437 out of 1,117 weeks—slightly more than one out of every three weeks (see Figure 9-3). <br /> The county been included in U.S. Department of Agriculture (USDA) drought disaster declarations in six <br />of the past seven years. <br /> The county has experienced seven significant multi-year droughts in the last 40 years (1980 to 2020), <br />amounting to a severe drought every 5 to 6 years on average. <br />Source: U.S. Drought Monitor <br /> <br /> Figure 9-3. Percent of San Mateo County Affected by Each USDM Rating, 2000 – 2021 <br /> <br /> <br />9-9