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<br />. <br /> <br />0755 <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />DETJ<.FiY1lNATION OF BASIN CHAf;ACTERISTICS <br /> <br /> <br />32. Storm studies. - The drainage area of the Purgatoire River is <br /> <br /> <br />small compared to the area covered by the air masses or synoptic situa- <br /> <br /> <br />tion under consideration. However, the topographic features within <br /> <br /> <br />and adjac.ent to the drainage area are of great importance to the major <br /> <br /> <br />storm rainfall within the basin. Analyses of rainfall records, in <br /> <br /> <br />Colorado and New Mexico, indicate that polymorphous storms occur within <br /> <br /> <br />the Purgatoire River Basin above Trinidad and that large magnitude <br /> <br /> <br />storms usually occur during the period from April through October. <br /> <br /> <br />33. After studying all storms of record in the general'vicinity <br /> <br /> <br />of Trinidad, it was found that the storm of June 2-6, 1921, which cen- <br /> <br /> <br />tered near Pueblo, Colorado, had produced precipitation of higher in- <br /> <br /> <br />tensity than any storm of record within a radius of 100 miles of the <br /> <br /> <br />drainage basin above Trinidad, and the secondary center which occurred <br /> <br /> <br />near Florence, Colorado, was the type of storm that could well be ex- <br /> <br /> <br />pected to occur over the. Purgatoire drainage area. Other storms of <br /> <br /> <br />record in the Hocky l'iountain ,(egion were also studied but it was deter- <br /> <br /> <br />mined that these storms, as modified by the effects inherent in trans- <br /> <br /> <br />position to the Purgatoire Basin would be less critical than the storm <br /> <br /> <br />of June 1921. <br /> <br /> <br />34. Storm transposition. The secondary center of the June 2-6, <br /> <br /> <br />1921 storm was transposed, without rotation, 85 miles south-southeast <br /> <br /> <br />and centered near Weston, Colorado, thus placing it in a critical <br /> <br /> <br />position on the watershed above Trinidad in accordance with basin <br /> <br /> <br />characteristics determined from a study of major storms which have <br /> <br /> <br />occurred over the basin. In transposing this storm to the most critical <br /> <br /> <br />position feasible above Trinidad, anadjust~ent of minus eight percent <br /> <br /> <br />was made for the effect of the inflow oarrier and it was determined that <br /> <br /> <br />the precipitation over areas above elevation 10,000 feet would not be <br /> <br />28 <br /> <br />APPENDIX B <br /> <br />