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irrigated" categories, AgStat corn statistics are only available for "total". Therefore, it is <br />likely that some of the discrepancy between the GIS coverages and AgStat estimates in <br />irrigated acres of the corn crop type maybe due to the inclusion of non-irrigated corn <br />acreages in AgStats. <br />The GIS irrigated acreage coverages do not include irrigated parks, golf courses, open <br />spaces, or small hobby farms less than 3 acres (see RTi documentation) within the overall <br />boundaries of cities; this information is included in AgStats. This likely contributes to <br />the large discrepancies in counties encompassing municipalities, such as Arapahoe, <br />Douglas, and Jefferson. <br />Table 1. GIS Acreage as a Percent of AgStat Acreage by County by GIS Year <br /> Year <br />Coun 1976 1987 2001 <br />Adams 80% 81% 71% <br />Ara ahoe 23% 20% 17% <br />Boulder 92% 100% 90% <br />Clear Creek 38% 31% 3% <br />Elbert 50% 61% 24% <br />Dou las 43% 63% 17% <br />Jefferson 58% 62% 54% <br />Larimer 73% 84% 84% <br />Lo an 81% 86% 66% <br />Morgan 90% 116% 87% <br />Park 77% 62% 52% <br />Sedgwick 49% 50% 37% <br />Washin ton 20% 25% 13% <br />Weld 88% 99% 91% <br />Basin Total 80% 90% 75% <br />Water Rights Analysis -Approach and Results <br />Changes in crop type and irrigated acres based on the relative priorities of several ditches <br />were evaluated. Using information from HydroBase, senior and junior water rights were <br />reviewed to determine whether changes in irrigated acres of individual crop types from <br />the GIS irrigated acreage assessment were dependent on water rights priority. In Figures <br />9 and 10, the general trends for Boulder County Agstats (left axis) are compared to the <br />percentage changes in crop type at the ditch level (right axis) for two senior and two <br />junior water rights, respectively. In Figure 9, the senior Howell Ditch (WDID 0600536) <br />changed from a mix of 62% alfalfa and 38% pasture in 1976 to 100% alfalfa in 1987 to <br />100% pasture in 2001. The total acreage under this ditch remained constant at 103.5 <br />acres. Over this same time period, the senior Chapman McCaslin Ditch (WDID <br />0500546) changed from a mix of 85% pasture, 8% corn and 7% alfalfa in 1976 to 7% <br />pasture, 3% corn, 85% alfalfa, and 6% small grains in 1987 to 75% pasture, 11% corn, <br />and 14% alfalfa in 2001. The total acreage under this ditch remained constant at 258 <br />Page 6 of 11 <br />