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<br />-12- <br /> <br />-13- <br /> <br />southwestern Colorado. After passing over numerous mountain barriers, <br />the moisture content is normally depleted by the time the air mass <br /> <br />long-term rainfall records have not been kept in the Gore Creek <br />Valley. Consequently, it was necessary to use data from one or more <br />of the available stations for developing rainstorm data for the Gore <br />Creek Valley. Elevation and both orographic and geographic orien- <br />tation of these gaging stations are very important since the elevation <br />and temperature limits the amount of moisture available to a thunder~ <br />storm. The orographic character helps determine the potential uplift <br />and the geographic orientation determines the degree of protection <br />from moist air masses. The Dillon precipitation data was determined <br />to be the most nearly representative of the records available, con~ <br />sidering the above. enumerated factors. <br />Analyses have been made of the Dillon rainfall data for storms <br />that could be identified as thunderstorms (Figure 111-2). These <br />analyses show the one~percent probability, 24-hour precipitation to <br />be 1.85 inches and the ten-percent, 24-hour value to be 1.07 inches. <br />A portion of this precipitation usually <br /> <br />falls as hail pellets or <br />11,000 feet. 1.2 <br /> <br />reaches the Gore Creek basin. <br /> <br />RilinfallPrecipitation <br />Rilinfall in the Gore Creek Valley can be either the more common <br />thunderstorm or the infrequent general type storm. <br />The thunderstorms occur most frequently and with greatest in- <br />tensity in July and August. These storms deliver the majority of <br />their precipitation in a time span of about 25 minutes.7 Amounts of <br />precipitation generated from these storms in the Gore Creek basin are <br />somewhat smaller and the intensity is less than those occurring at <br />lower elevations due to the lesser amount of moisture available at <br />the lower temperatures, higher elevations and the protection of the <br /> <br />~rea from available moisture sources. <br /> <br />Detailed examination of the available records for an indication <br />of rainfall induced snowmelt produced little indication of this phe- <br />nomena being critical in the higher le~els of the Central Rockies. <br />This is attributed to the fact that temperatures in May and early <br />June in the Gore Valley are normally too cold to pro~ide enough <br />upliftforathundcrstOnl1. For the cases where precipitation occur- <br />red in the form of ,;now or sleet at higher ele~ations and r~in at <br />the lower, the results were to increase the snowpack depth in the <br />high elevations and the snowpack water content in the lower ele~ations. <br />The records show that the streamflow discharge usually drops signifi- <br />cantly on day, with precipitation because the associated temperature <br />dropreduce,the,nownle1ting. <br /> <br />graupel, especially at ele~ations abo~e <br />Examination of sixteen precipitation records taken from the Gore <br />Creek and Eagle Ri~er Valley stations for summer and fall months indi_ <br />cates that 68% of the daily or 24-hour precipitation would occur <br />during a thunderstonn. The remaining 32% of the rain typically falls <br />in light showers after the cell dissipates and later in the day. <br />Comparisons of the 68% value and the Weather Bureau time distribution <br />in TP_4021 of 80%-90% resulted in using a compromise value of 81%. <br /> <br />Study of the records also indicates the areal distribution of the <br />