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SECTION 6: DROUGHT <br />EXTENT <br />The Palmer Drought Index is used to measure the extent of drought by measuring the duration <br />and intensity of long-term drought -inducing circulation patterns. Long-term drought is cumulative, <br />with the intensity of drought during the current month dependent upon the current weather <br />patterns plus the cumulative patterns of previous months. The hydrological impacts of drought <br />(e.g., reservoir levels, groundwater levels, etc.) take longer to develop. Table 6-2 depicts <br />magnitude of drought, while Table 6-3 describes the classification descriptions. <br />Table 6-2. Palmer Drought Index <br />-2.75 and <br />-2.00 to <br />-1.25 to <br />-1.24 to <br />+1.00 to <br />+2.50 to <br />Abnormally Dry <br />fire risk above average. Coming out of <br />-1.9 <br />drought: some lingering water deficits; <br />n/a <br />below <br />-2.74 <br />-1.99 <br />+.99 <br />+2.49 <br />+3.49 <br />-2.0 to <br />-4.00 and <br />-3.00 to <br />-2.00 to <br />-1.99 to <br />+2.00 to <br />+3.00 to <br />+4.00 and <br />below <br />-3.99 <br />-2.99 <br />+1.99 <br />+2.99 <br />+3.99 <br />above <br />-4.00 and <br />-3.00 to <br />-2.00 to <br />-1.99 to <br />+2.00 to <br />+3.00 to <br />+4.00 and <br />below <br />-3.99 <br />-2.99 <br />+1.99 <br />+2.99 <br />+3.99 <br />above <br />Table 6-3. Palmer Drought Category Descriptionsz <br />2 Source: National Drought Mitigation Center <br />City of San Marcos I Hazard Mitigation Action Plan Update 2024 1 Page 3 <br />Going into drought: short-term dryness <br />slowing planting, growth of crops or pastures; <br />-1.0 to <br />Abnormally Dry <br />fire risk above average. Coming out of <br />-1.9 <br />drought: some lingering water deficits; <br />pastures or crops not fully recovered. <br />Some damage to crops, pastures; fire risk <br />Moderate Drought <br />high; streams, reservoirs, or wells low, some <br />-2.0 to <br />water shortages developing or imminent, <br />-2.9 <br />voluntary water use restrictions requested. <br />Crop or pasture losses likely; fire risk very <br />-3.0 to <br />Severe Drought <br />high; water shortages common; water <br />-3.9 <br />restrictions imposed. <br />Major crop/pasture losses; extreme fire <br />-4.0 to <br />Extreme Drought <br />danger; widespread water shortages or <br />-4.9 <br />restrictions. <br />Exceptional and widespread crop/pasture <br />Exceptional <br />losses; exceptional fire risk; shortages of <br />_5.0 or less <br />Drought <br />water in reservoirs, streams, and wells, <br />creating water emergencies. <br />2 Source: National Drought Mitigation Center <br />City of San Marcos I Hazard Mitigation Action Plan Update 2024 1 Page 3 <br />