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<br />In most cases, the former technique will be used, because only temper- <br />ature and precipitation data are required, and the technique has proven <br />to be relatively satisfactory. <br />c. Develop a relationship of maximum temperature vs. duration <br />that envelops maximum values recorded during past snowmelt seasons. <br />Values of temperature should be expressed for this purpose in degrees <br />above nOl'llllll for each calendar day, using a SlltOOth curve of normal <br />temperature vs. time. If the energy-budget method of snowmelt compu- <br />tation is used, derive corresponding maximum values of ather melt <br />variables such as wind and solar insolation. <br />d. In many cases, the II10St severe snowmelt runoff occurs if low <br />temperatures prevail during the early part of the snowmelt season when <br />normal temperatures are low and then extremely high ~eratures fol- <br />low. By a series of approximations, derive a temperature sequence (and <br />corresponding sequences of other melt factors if the energy-budget <br />method is used) that results in the most severe runoff computed in <br />accordance with the following step. Determine also the -.ximum preci- <br />pitation that would occur in the melt season consistent with these melt <br />factors. <br />e. Taking account of different temperatures in different elevation <br />zones, compute snowmelt during each computation interval of the storm <br />period in accordance with techniques described in Section 2.07 and add <br />any precipitation that falls as rainfall. Develop unit hydrograph, <br />loss rate and base flow criteria as described in paragraph 3.0ge and <br />apply to the snowmelt and rainfall totals for each period using tech- <br />niques described in Volume 4 in order to obtain the standard project <br />snowmelt hydrograph for each sub-area. Route and combine sub-area <br />hydrographs as described in paragraphs 3.09f and g. <br /> <br />3-17 <br />