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Vallejos Creek 33.69 <br />Upper Clover Creek 5.45 <br />Upper San Luis Creek 224.02 <br />Upper Saguache Creek 205.43 <br />Upper La Garita Creek 40.24 <br />Upper Carnero Creek 89.36 <br />West Indian Creek 41.63 <br />Upper Sand Creek 30.85 <br />Upper Ute Creek 30.01 <br />Ojito Creek 13.50 <br />Mendano Creek 36.90 <br />Zapata Creek 19.06 <br />Upper Sange de Cristo Creek 94.65 <br />Upper Ventero Creek 60.48 <br />Brook Creek 4.07 <br />Upper Rock Creek 17.44 <br />Raton Creek 21.84 <br />Average Annual Precipitation <br />In addition to drainage area information, the proration calculations for ungaged baseflow <br />locations require average precipitation values at both gage stations and ungaged locations. These <br />were developed using isohyetal precipitation maps for Colorado Water Division 3 <br />(precip_d3.shp) and for New Mexico (nm_ann.shp). These ArcView files were imported into <br />MapInfo for the analysis process. The New Mexico isohyetal contour ranges also required <br />conversion from contour lines into contour regions. <br />The analysis process to determine average precipitation in each delineated drainage area involved <br />first overlapping isohyetal GIS coverage onto the polygon coverage of the basin drainage areas. <br />This step was necessary to calculate the weighted average annual precipitation for each of the <br />areas. <br />For QA/QC purposes, two different methods were used during the analysis process to compute <br />average annual precipitation for each drainage area. In the first method, a proportional overlap <br />query was run in MapInfo that returned data on the proportion of isohyetal areas to drainage <br />areas. This data table was then exported from MapInfo to MS Excel, where the weighted <br />proportional overlap data was tabulated and summed for each drainage area using Excel pivot <br />tables. Average annual precipitation for each drainage area was also computed using a MapInfo <br />update column script (similar to the ArcView Avenue script developed during CRDSS). The <br />results from applying these two methods were then compared and indicated minimal differences <br />(less than 0.5 %). <br />The results of applying the MapInfo column script methodology are shown in Tables 3 and 4 for <br />gaged and ungaged locations, respectively. As with drainage areas, the average precipitation <br />values shown for ungaged locations represents the incremental area between the ungaged point <br />and upstream gage stations (if any). <br />C:\cdss\Task6-l.doc Drainage Areas and Proration Factors November 4, 1999 -Page 5 of 11 <br />