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coverage) using heads-up digitizing. The revised theme was then copied to a new <br />coverage called 96sprink for use in preparing the sprinkler extent coverage for the <br />previous year of mapping (1996). The new coverage for 1996 was then compared to <br />the RGWCD map of sprinkler extent for 1996 and sprinklers were added or <br />subtracted to reflect the RGWCD map. The 96sprink coverage was saved and used <br />as the base for modifications for the previous year where sprinkler coverage was <br />available (1993). This process continued until all 14 maps were represented by <br />ArcView coverages. <br />4. An ArcView script (modfind) was developed that performs intersections between the <br />irrigated parcel coverage and ditch service area coverage. The script assigns ditch <br />systems, and the percent of the parcel covered by the ditch system, as attributes to the <br />irrigated parcel coverage. The script was used during the irrigated acreage <br />assessment, and is described in the Irrigated Lands Assessment Report, prepared by <br />Agro Engineering. The modfind script was used to associate sprinkler irrigated <br />acreage to ditch systems for each of the 14 years with ArcView sprinkler coverages. <br />5. The resulting attribute table for each sprinkler coverage was exported from ArcView <br />to acomma-separated file with the name of the sprinkler extent coverage and a .txt <br />suffix (i.e. sprink98.txt). <br />6. A BASIC language program (sprink.bas) was developed that takes the sprinkler <br />extent coverage tables (i.e. sprink98.txt) and summarizes, by ditch system (or parcel <br />for ground water only lands), the acreage estimated to be covered by sprinklers in a <br />year. For years during the 1950 through 1998 period where sprinkler extent maps <br />were not available, linear interpolation was used between surrounding years of data. <br />1998 estimates of sprinkler acreage were used to represent 1999 through 2002 <br />sprinkler acreage. Sprinkler installation generally started around 1970 in the San Luis <br />Valley. Therefore, values for 1971 through 1974 were linearly interpolated from a <br />zero value in 1969 and the sprinkler extent determined from the 1975 map. <br />7. The result of this program was a file (sprinko.txt) that contains values of estimated <br />sprinkler extent acreage by ditch system (or parcel for ground water only lands) and <br />by year. This file was then input into the well processing program (wellproc.bas) <br />used to create the annual time series data input file. <br />As noted, sprinkler irrigation did not become a common practice in the San Luis Valley <br />until the early 1970s. The installation of sprinklers rose sharply during the 1970s, and <br />continued a steady incline through 1998. Figure 2 shows the estimated acreage irrigated <br />with sprinklers from 1950 through 2002. Also shown is the estimated total irrigated <br />acreage for the time period. <br />C:\Projects\rgdss\finemos_2004\appendA_cropcu_6-2004.doc A-7 of A-10 June 2004 <br />