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<br />23 <br /> <br />review of the project. This review and verification phase took place <br />over a 6-month period and resulted in a few minor modifications to the <br />overall precipitation pattern. This phase also included verification of <br />suspect data sets where station locations .and measurement techniques <br />were questioned. An effort was begun to use vegetation analysis and <br />satellite imagery from LANDSAT to confirm contour placements in parts of <br />western Co] orado. The time, effort and cost of undertaking this <br />approach was found to exceed the project resources. <br />In September 1983 the completed 1951-80 isohyetal analysis was <br />delivered to the U. S. Department of the Interior Geological Survey <br />Colorado District Offices at the Denver Federal Center. All of the <br />final drafting and color work in preparation for publication was done in <br />their facilities. The printing itself was done by the U. S, Geological <br />Survey National Mapping Division in Reston, Virginia. <br />B. Comparison with the 1931-1960 map <br />There are a number of differences between the old 1931-1960 <br />i sohyetal map and the new 1951-1980 analysis. For the most part, the <br />differences are small both in area and magnitude. Many small changes <br />were made in local areas where single contours were moved short <br />distances, There were only a handful of systematic changes that <br />affected areas greater than a few square miles. Changes from the <br />original map resulted mostly from having recent data in areas where <br />1 ittle or no measured data were available 20 years ago. Changes were <br />al so a resul t of differences in the measured averages from one period to <br />the next or differences in the interpretation and analysis of the data. <br />Areas where changes were made from the 1931-1960 averages that <br />affect sizeable areas are shown in Figure 6. The largest single change <br />