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from the web site at www.ftw.nres.usda.gov/statsgo_ftp.html. The three tables and <br />associated fields used in the available water capacity analysis are: <br />Comp.dbf - This table indicates the percent (field compct) of the Muid with a <br />specific soil type (field Muidsegnum). <br />Compyld.dbf -This table indicates soil types (fieldMuidsegnum) that are cultivated <br />with crops (field Cropname) and yields (fields Nirryld and Irrylc~. <br />Layer.dbf - This table provides minimum (field Awch~ and maximum (field <br />Awch) water holding capabilities for a depth range (field Laydepl to <br />field laydeph) of a soil type (field Muidsegnum). <br />In ArcView, the tables indicated above were linked to create a new table (named <br />t'layer~ that had informati on needed to estimate the average water holding capacity <br />in each soil polygon. The following table processing occurred. <br />a. The layer.dbf table was linked with the ~oils'inap attribute table (link field <br />Muid, the ~oils'~olygons selected, and th e resultant selected records in the <br />layer.dbf table saved into a new table (t'layer~. The tla yer table contains records <br />only for soils found in the Rio Grande Basin. <br />b. The tlayer table was joined with the Comp.dbf"table (join field Muidsegnum) <br />such that the percent of each soil type in a Muid was added to the tlayer table. <br />c. Anew numerical column (field include) was added to the tlayer table to indicate <br />whether a soil type (field Muidsegnum) should be included in the available water <br />capacity calculation. This column was completed by the following process. <br />- Soil types with names of Rock Outcrop" or Rubble Field" were not included <br />(include=0). This was performed using the ArcView query and calculate <br />functions. <br />- The tlayer table was linked with the Compyld"table (link field <br />Muidsegnum), Compyld records selected and associated records in the j oined <br />table included in the analysis (include=l). Due to the primary purpose of <br />calculating available water capacity for application in crop consumptive use <br />calculations, this process bases the available water capacity for aMuid on <br />cultivated lands if they exist in aMuid. Of the 26 map units in the Rio Grande <br />Basin, 15 included cultivated soils. <br />- For the ll Muids without cultivated lands, the remaining (after exclusion for <br />rock outcrops) soil types were included in the analysis. <br />4. In Excel, a worksheet (dwc.xls~ was prep ared to accept the tlayer table created in <br />the previous step. Formulas were added to the worksheet to summarize the average <br />soil water capacity for depth zones of 0-12 inches, 12-24 inches and 24-60 inches in <br />each map unit. An average of the high and low water holding capacities for a given <br />soil type in a given depth range was assumed to be representative of the water holding <br />capacity. Also calculated was an average available water capacity (AWC) in inches <br />per inch for the first 60 inches of soil. A summary table in the worksheet was <br />prepared containing the Muid and AWC and saved in text format. <br />appendC_cropcu.doc C-2 of C-4 June 5, 2000 <br />