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<br />12 <br /> <br />~....~ <br /> <br />HYDROLOGIC AND HUMAN ASPECTS OF THE 1976-77 DROUGHT <br /> <br /> <br />May 1, 1976 <br /> <br />August 2B, 1976 <br /> <br />B <br /> <br />Oct. 30, 1976 <br /> <br />c <br /> <br />D <br /> <br />Above +4 Extreme <br />+ 3 to +4 Severe <br /> <br />+2 to +3 Moderate <br />-2 to +2 Near normal <br /> <br />EXPLANATION <br />-2 to -3 Moderate drought <br />-3 to -4 Severe drought <br /> <br />National Weather Service, NOAA <br />Below -4 Extreme drought <br />Values indicate departures from normal clima,te <br /> <br />Figure 6. Maps of the United States showing values of Palmer index on four selected <br />dates in 1976. <br /> <br />the drought areas and either ended or inter- <br />rupted the drought. <br />Maps of the Palmer index for intermediate <br />dates show continually changing patterns and <br />values in response to rainfall, temperature <br />changes, and other factors. A drought is a <br />dynamic condition in time, space, and severity. <br />It is the variations, sometimes only nuances, <br />that change opinions about a drought and <br />affect decisions on courses of action that <br />might be taken to counteract drought. <br />Another ramification relates to a multiyear <br />drought and its effect in a basin with storage <br />facilities as opposed to one without. The <br />former may have more serious problems than <br />. the latter because a larger part of the annual <br />yield is used in a basin where water can be <br />stored than in one where there is only natural <br />flow. <br /> <br />The use of stored water during the first <br />year or so of a drought is a normal operating <br />procedure. Examples given later in this report <br />show that releases of stored water in parts of <br />the Western States in 1976 benefitted the <br />consumer but led him to the conclusion that <br />there was not a serious drought. Since 1977 <br />was also very dry, stored water was depleted <br />in' some reservoirs and reached dangerously <br />low amounts in others. Fortunately, 1978 was <br />a wet year; otherwise, even more serious <br />water-supply problems would have occurred. <br />The reasons for multiyear drought problems <br />in basins that have been developed extensively <br />for reservoir storage are manifold and <)om- <br />plex. Some releases from storage are man- <br />dated by operating rules, see section on Legal <br />Aspects; some are made to supply consumptive <br />uses which generally are greater than in an <br />