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<br />000948 <br /> <br />Table 2 <br />Principal Steps in Revision of Yampa River Baseflows <br /> <br />1. Using ARCVIEW, create an environment with the following themes (layers) for the Yampa <br />River Basin. <br />Basin Boundary for Yampa River Basin (extracted from CRDSS Basins Layer) <br />CRDSS Isoheytal Map for West Slope. <br />Contour Map for West Slope. <br />Base flow nodes for the Yampa as taken from Joanna Daniels work. <br />Diversion headgate locations for the West Slope. <br />To make the spatial processing more efficient, the Isoheytal Map was cut at the basin <br />boundary by using the Fmdarea script. The Findarea Avenue script in ARCVIEW was written <br />by Ross Bethel to create new polygons from the intersection of two polygons. Though it was <br />written with the idea of determining the characteristics of isohyetal polygons in a given <br />drainage basin, it may also be used to make new isohyetaIs polygons just within the basin <br />boundary. See a later section for more description of the Findarea Script. <br /> <br />2. IdentifY in the ARCVIEW environment the baseflow nodes named in the Phase II Yampa <br />River ModeL If the baseflows are not identified on the baseflow node layer, use the diversion <br />headgate location layer to identifY a baseflow point. Use the Polygon Draw function of <br />ARCVIEW, with the contour and base flow node layers visible, to outline the contributing <br />basin to each baseflow point. Attach these polygons to a new theme (we called ours <br />"Drain"), add a column to the table associated with that new theme and place the Baseflow <br />identifier in that column. <br /> <br />3. After finishing the drawing of the drainage basins, make that theme editable and copy the <br />graphic features from that "Drain" layer to the Yampa Basin Isohyetal theme. Then modify <br />the table associated with the Isohyetal theme by adding columns for "Basin", "Recnum", and <br />"Newarea". In the "Basin" field fur the new polygons, number them sequentially starting with <br />101. Find the script "recnum", change the filename in the script to be consistent with your <br />isohyetal theme name and then execute that script. That script will sequentially number the <br />recnum field for use in the next process. <br /> <br />3. Find the script "Findarea" and change the theme name to that of the isohyetal theme that <br />includes the new drainage polygons. Check the field names like Basin, recnum and newarea <br />for consistency between the script and the polygon table. Run the script. This places new <br />polygons at the bottom of the table representing the intersections between the isohyetals and <br />the drainage basins and labels those polygons with the basin id (Le. 101 and the precip id). <br /> <br />4. Save this layer into a new theme (with create shapefile) and delete the rows in this new <br />themes table related to the original isohyetals and drainage basins, leaving just the new <br />polygons realted to the intersections of the isohyetals and drainage basins. Save the table in <br />text furmat to a file (we called ours "predrain.txt". Save also the table with node identifiers <br />(associated with the theme that just contains the drainage basins) to a text file, we called ours <br />"drain.txt". <br />