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<br />used to compute the mathematical precipitation mean for use in NOAA frequency <br />distribution. The NWS and UWUA data agreed closely. The NOAA data, however, <br />indicated greater rainfall. This fact is 1 ilke"y attriblJtable to additional <br />con;ervatism, including the shorter time span for computing the mean (resulting <br />in i larger standard deviation). Figure 3 i'llustrates the 24 hour rainfall <br />fre~uency relationship for the UWUA and NWS data, as well as the NOAA <br />inflJrmation. Figure 4 illustrates rainfall depth frequency for several durations <br />basl~d on the UWUA record. <br />Due to the close correlation of the l"ecords '6vailable from the UWUA and <br />NWS, the rainfall frequency relationships developed from the UWUA l.ecord <br />analysis were used for the lower basin. The NOM data was used to define the <br />rainfall for the :Jpper basin, where other data was not available. The rain- <br />fall ~Ias then graduated between these two areas for the intervenin9 basins. <br />The rainfall data reflects rain precipitation and does not include snowfall. <br />Statistically, the results'of analyzed data is more reliable when segregated <br />into individual hydrologic families (rain, snow). Consistent with the NOAA <br />procedure, precipitation data has been analyzE!d using precipitation records <br />from ~'ay 1 to October 1. Individual storms nE!ar these t'ime boundari es have <br />been checked to assure a reliable separation of rain and snow data. Such <br />definition is also consistent with meteorologiciilly probable moisture sources <br />resulting in rainstorms. <br /> <br />. <br /> <br />7 <br />