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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />5.0 ESTIMATE OF IRRIGATED LANDS AND RELATED WATER USE <br /> <br />5.1 IRRIGATED LANDS <br />Beck (1967) estimated that a total of 70,000 acres were irrigated from both ground and surface <br />water sources in 1966. Based upon records from the Baca, Las Animas and Prowers County <br />Assessors Office, MWE (1999) reported a total of 106,300 acres of irrigated land within the <br />District and a total of 128,500 acres within the Basin. <br /> <br />Satellite imagery and GIS (ARC-VIEW) tools were used to compare the number of irrigated <br />acres at two different time periods, August 1989 and August 1999. Comparisons of the <br />interpretation for the two periods are summarized in Table 5-1 and are shown in Map 6. This <br />comparison confirms visible changes in the number of acres being irrigated, the portion of the <br />growing season the irrigation was used, and the type of irrigation methods utilized by irrigators. <br />A review of the satellite imagery indicates there were approximately 39,400 acres being irrigated <br />in 1989. Of this total, 10,400 acres appeared to have had winter wheat planted and already <br />harvested at the time the satellite image was taken. The remaining 29,000 acres were planted <br />to corn or other crops that were being irrigated during August 1989. A similar interpretation of <br />the August 1999 satellite imagery indicated there were approximately 94,600 acres being <br />irrigated. Of this total, approximately 18,100 acres were interpreted as already harvested and <br />assumed to be irrigated wheat. MWE interpreted the remaining acreage, 76,500 acres, to be <br />planted to corn or other crops that were being actively irrigated in August 1999. It should be <br />emphasized the difference in estimated acreage using the satellite imagery and the county <br />assessor acreage can be attributed to the lack of field verification of the satellite imagery. <br /> <br />For comparison purposes, MWE made a visual assessment, using infrared satellite imagery, of <br />a 100-square mile area southeast of Stonington to determine the number of center-pivot <br />sprinklers in place in August of 1989 versus August 1999. In August 1989 there were 14 center <br />pivots observed (14 pivots x 122 acres = 1708 acres) in the area; in August 1999 there were 57 <br />center pivots observed, including three center pivots covering full sections (54 pivots x 122 <br />acres + 3 pivots x 488 acres = 8052 acres). This visual comparison indicates there has been <br />both a change in the type of irrigation method being used and what appears to be a 3-fold <br />increase in the number of acres being irrigated by center pivots in this 100-square mile area <br />during the 10-year period. <br /> <br />The process used to make the comparison between the irrigated land in 1989 and 1999 was to <br />focus upon the shape and color of the parcels. Since center pivot sprinklers are circular, they <br />are readily identifiable when compared with the rectangular shapes of non-irrigated farmland. <br />The infrared satellite imagery results in any actively growing vegetation showing as a red shade <br />on the image. The more intensively the crop is irrigated, the redder it will appear on the image. <br /> <br />V-1 <br />