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91% with Colorado Agricultural Statistics for 1998. Classification techniques were used to <br />determine the crop type grown on each of these irrigated parcels. 13% of the irrigated lands were <br />classified as potatoes, 19% were classified as small grains, 1% were classified as vegetables, 23% <br />were classified as alfalfa, and 44% were classified as irrigated meadow. This estimate of crop type <br />agreed within 92% with the subset of ground-truthed data collected by the Rio Grande Water <br />Conservation District. <br />An additional 12,525 acres in 47 parcels were classified as "user defined as irrigated meadow". <br />These parcels were reported by water users as being irrigated. However, they represent water short <br />parcels whose spectral response and consumptive use characteristics more closely resemble one of <br />the native land classes instead of the irrigated meadow classification and were consequently <br />assigned to one of the non-irrigated classes. <br />The irrigated parcel theme was developed byhand-digitizing the parcel boundaries from the satellite <br />imagery. This theme represents the total amount of acreage that was actually irrigated during the <br />1998 growing season. Irrigation was defined as the purposeful act by man to divert water and place <br />it to a beneficial use for the growing of crops. A total of 10,213 parcels covering 612,739 acres were <br />classified as irrigated. Irrigated parcels were defined as contiguous areas of land cropped by a single <br />crop type under a single irrigation system. A series of database attributes were associated with each <br />irrigated parcel, including crop type, irrigation system type, parcel area, perimeter, x centroid, y <br />centroid, the water district, county, and hydrologic unit code. If the parcel was located within the <br />service area of one or more ditch systems, each ditch system was assigned to the parcel. <br />In terms of water supply, 91.6% of the acreage in these irrigated parcels was within the service area <br />of one or more ditch systems and were estimated to have surface water available. 62.7% of the <br />acreage within these irrigated parcels was identified by the Spatial Data Contractor as having ground <br />water available. 36.8% of the irrigated acreage was served by surface water only. 7.9% of the <br />irrigated acreage was served by ground water only. 54.8% of the acreage in the irrigated parcels had <br />both surface and ground water available. 0.5% of the acreage in the irrigated parcels had an <br />unknown water supply. In terms of irrigation system type, sprinklers irrigate 44.5% of the irrigated <br />acreage in the basin. The remaining 55.5% of the irrigated acreage is irrigated by flood. The <br />Irrigated Parcel Theme is displayed in Figure 10 of this report. <br />Land Cover Classification Theme. Aland cover classification theme was developed to indicate <br />the land cover class of both irrigated and non-irrigated lands within the ground water model area of <br />the San Luis Valley floor. This theme, which recognized nine non-irrigated land cover classes and <br />five irrigated land cover classes, is intended to assist in determining native vegetation consumptive <br />use for the areas of the basin that are not irrigated. 1,395,575 acres within the 1,988,861 acres of the <br />ground water model area were classified asnon-irrigated for 1998. 4.9% of the acreage within the <br />ground water model area was classified as non-irrigated meadow, 21.4% was classified as heavy <br />native vegetation, 9.7% was classified as medium native vegetation, 26.7% was classified as sparse <br />native vegetation, 2.3% was classified as bare ground, 1.9% was classified as deciduous trees, 3.0% <br />was classified as coniferous trees, 0.1% was classified as hydrophytes, and 0.2% was classified as <br />open water. The remaining 29.8% of the acreage within the ground water model area was assigned <br />2 <br />