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the-other hand the CAS data were determined to be a poor indicator of historic irrigated <br />meadow in the basin. This is because the amount of harvested irrigated meadow may <br />vary greatly from year to year, while the amount of irrigated meadow generally does not. <br />Therefore the amount of irrigated meadow each year is estimated to be constant. Note <br />that in water short years, less water is likely applied to irrigated meadow than cash crops <br />grown under the same ditch. CAS estimates were not available for the small percentage <br />of vegetables grown in the San Luis Valley; therefore the amount of vegetables each year <br />of the analysis was estimated to be constant. <br />The following example illustrates the process used to estimate the irrigated acreage time <br />series for a sample structure (Ditch "X") in 1992. Table 4 shows example CAS crop <br />acreage for county "A" for two years, 1992 and 1998. Also shown is the 1998 acreage <br />for the sample structure (Ditch "X") from the irrigated acreage assessment (IAA). In this <br />example, all the acreage served by Ditch "X" is in County "A". Small grains, potatoes, <br />and alfalfa are referred to as "Time-varying Crops" in this example. <br />Table 4 <br />Example Acreage Estimates <br /> Coun t "A" Ditch "X" <br />Crop Category 1992 CAS 1998 CAS 1998 IAA <br />Small Grains (Barley, <br />Oats, and Wheat <br />12,000 <br />12,500 <br />2,000 <br />Potatoes 6,000 7,500 500 <br />Alfalfa 12,000 11,000 800 <br />Sub Total 30,000 31,000 3,300 <br /> <br />Irrigated Meadow N/A N/A 2,000 <br />Vegetables N/A N/A 20 <br />Total N/A N/A 5,320 <br />1. Determine Total Acreage of Time-varying Crops. Colorado Agricultural Statistics <br />acreage for crop types barley, oats, wheat, alfalfa, and potatoes were combined for <br />1998 and 1992. The acreage assigned to small grains, potatoes, and alfalfa for the <br />sample structure during the 1998 Irrigated Acreage Assessment were combined. <br />1998 County "A" CAS Subtotal = 12,500 + 7,500 + 11,000 = 31,000 acres <br />1992 County "A" CAS Subtotal = 12,000 + 6,000 + 12,000 = 30,000 acres <br />1998 Ditch "X" Subtotal = 2,000 + 500 + 800 = 3,300 acres <br />2. Determine Total 1992 Sample Structure Acreage for Time-varying Crops. The <br />estimated sample structure acreage for time-varying crops in 1992 is the 1998 <br />structure acreage from the irrigated acreage assessment (3,300) prorated by the ratio <br />of total county acreage in 1992 (30,000) to the total county acreage in 1998 (31,000). <br />1992 Subtotal for Sample Structure = 3,300 x (30,000 / 31,000) = 3,194 acres <br />C:\Projects\rgdss\finemos_2004\appendA_cropcu_6-2004.doc A-4 of A-10 June 2004 <br />