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<br />IV. DESCRIPTION OF MAY..,JUNE 1973 FLOOD <br /> <br />11 . METEOROLOGY, CLIMATOLOGY, AND HYDROLOGY <br /> <br />a. General. The data presentE,d 1.n this section provIde a <br />narrative description of the mete<lrological, climatological, g,nd <br />hydrological characteristics of the :flood period. The peak dis- <br />charge and hydrograph data presented were furnished by the United <br />States Geological Survey and by Stat.e agencies and are prelimInary <br />in nature. Discharge information from some gaging stations in the <br />basin is not yet available. The :lnformation presented does, <br />however, provide !In understanding of the events >'hich produced <br />the flood, the relative magnitude of the event, and the eff'ects <br />of reservoir regulation on flows :In the Platte River basin. <br /> <br />b. Mountain snow. The mountaIn snowpack over the South <br />Platte River and North Platte River basins in Colorado and <br />Wyoming was, in general, slightly below normal at the beginnIng <br />of April 1973, but it increased substantially during April. By <br />1 May 19'73, the mountain snowpack w,s well above normal OVE,r <br />both basins, Over certain tribut!tr:l,es of the North Platte River, <br />in the ioountain area between Casp.~r .lOd Laramie, Wyoming, t.he <br />snow cover increaned in April and ea,rly May to more than 200 <br />percent of averag.!. Table 1 sUll1mar1.zes the lI10untain sn""'pl,clt <br />data. <br /> <br />Table 1 <br />SUMMARY OF illUNTAIN SN01-1 MEASUREMEN'J:'S <br />(1973 sno~' water content ItS percent of average) <br /> <br />1 April <br /> <br />L~x: <br /> <br />South Platte River (Colorado) <br />North Platte River (Wyoming) <br /> <br />135 <br />100 <br /> <br />130 <br />1~)0 <br /> <br />c. Snowmelt runoff from the lower elevations of the Eiouth <br />Platte River and North Platte River basins began about the middle <br />of April. Dur1.ng early to mid-Ma:r, a >reek of warmer than nonnal <br />temperatures init:lated snowmelt runoff from the higher e.le''atIons. <br />Table 2 presents mountain snow-coure,e water content on 1 Me.y In <br />tributary basins of the South Pl.atte and North Platte Rivers. <br />The 1953-67 average conditions, f,)1" the stations where recclrcls <br />are available, ar.! also shown in -thE' table. These data indica,te <br />that water content of the 1 May 197:1 snowpack over the tributa,ry <br />basins of the two rivers, as sh0W11 J.n ta'ble 2, varied from about <br />normal to 170 peI'{,ent above normal. <br /> <br />]< <br />,j <br />