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<br /> <br />2021 Multijurisdictional Local Hazard Mitigation Plan <br /> <br />9.2.5 Severity <br />The severity of any given drought depends on the degree of moisture deficiency, the duration, and the size and <br />location of the affected area. The longer the duration of the drought and the larger the area impacted, the more <br />severe the potential impacts. <br /> <br />U.S. Drought Monitor Ratings <br />San Mateo County has a history of severe droughts. As shown in Figure 9-3, at least part of the county has <br />experienced extreme (D3) or exceptional (D4) droughts more than once since 2000. <br /> <br />Drought Impact Reporter <br />The National Drought Mitigation Center developed the Drought Impact Reporter in response to the need for a <br />national drought impact database for the United States. Information comes from a variety of sources: on -line, <br />drought-related news stories and scientific publications, members of the public who visit the website and submit a <br />drought-related impact for their region, members of the media, and staff of government agencies. The database is <br />being populated beginning with the most recent impacts and working backward in time. <br /> <br />The Drought Impact Reporter indicates 1,208 impacts from drought that specifically affected San Mateo County <br />from January 2011 through May 2021, 90 percent of them based on media reports (Drought Impact Reporter, <br />2021). The following are the reported numbers of impacts by category (some incidents are assigned to more than <br />one impact category): <br /> Agriculture—287 <br /> Business and Industry—99 <br /> Energy—11 <br /> Fire—190 <br /> Plants and Wildlife—324 <br /> Relief, Response, and Restrictions—545 <br /> Society and Public Health—316 <br /> Tourism and Recreation—122 <br /> Water Supply and Quality—686 <br /> <br />9.2.6 Warning Time <br />Predicting drought depends on the ability to forecast precipitation and temperature. Scientists currently do not <br />know how to predict drought more than a month in advance for most locations. Only generalized warning can <br />take place due to the numerous variables that scientists have not pieced together well enough to make accurate <br />and precise predictions. <br /> <br />Determination of when drought begins is based on impacts on water users and assessments of available water <br />supply, including water stored in reservoirs or groundwater basins. Different water agencies have different criteria <br />for defining drought. Some issue drought watch or drought warning announcements. <br /> <br /> <br /> <br />9-10