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MEMO 93 <br />For the North Park portion of the SPDSS study area historic irrigation records were obtained from the <br />District 47 water commissioner in addition to several sets of aerial photos from 1950s and 1969. The <br />imagery and irrigation records were used irrigated lands mapping. Specifically, historic irrigation records <br />were used to edit 2001 mapping results as described in SPDSS Technical Memorandum 91, Appendix H, <br />and the aerial photos as described in Section 4.1.2.2 of this memo. However, as evidenced by the historic <br />irrigation records and aerial imagery, irrigation in the North Park area has shown little change since the <br />1950s. <br />3.2 Agricultural Statistics <br />The USDA's National Agricultural Statistics Service (NABS), and the Colorado Agricultural Statistics <br />Service (CABS) both report annual agricultural statistics for all reported irrigated crops by county dating <br />historically to 1909. Data from HydroBase was summarized by the Consumptive Use (CU) contractor <br />and provided to RTi for each crop type within all SPDSS counties (SPDSS Task 71). For counties lying <br />partially within the SPDSS study area (Sedgwick, Logan, Washington, Logan, Elbert, El Paso, Teller, and <br />Park), the percentage of irrigated agriculture in the SPDSS area was estimated and used to prorate the <br />agricultural statistic totals within these partial counties. Figure 4 shows the decadal trends of the <br />agricultural statistics reported acreage within SPDSS counties for the years 1950 thru 2001. <br />o° <br />~°°~ <br />o° <br />3~'°~ <br />o° <br />d 3~°~ <br />o00 <br />a ~~° <br />o° <br />ti°~~ <br />o° <br />o ~,.. <br />.. <br />~.~°' o _- <br />o ,~ 3 .:..- -_ ~-- <br />~~~o ~. <br />o° <br />goo <br />~ 1950 1960 1970 1980 1990 2000 <br />Decade <br />Alfalfa Beans Corn Small Grains <br />Sugar Beets Sunflowers Grass Pasture Vegetables <br />Figure 4. Agricultural statistics decadal total acreage per crop type within SPDSS, 1950 - 2001 as compiled <br />from NASS and LASS data by the SPDSS CU contractor. <br />Likewise, Appendix Tables B.1 - B.4 summarize the estimated agricultural statistics for 2001, 1987, <br />1976, and 1956. The agricultural statistics are a useful indicator of crop production within a county for a <br />given time period. Although agricultural statistics are reported annually, there are errors in the data set. <br />Prior to 1987, irrigated acreage of alfalfa was not fully reported each year. Likewise, prior to 1986, grass <br />pasture also was not fully reported each year. Both Figure 4 and Appendix Tables B.3 and B.4 highlight <br />the absence of full reporting for all crops in 1976 and 1956. In addition to missing data, some acreage <br />reported within the agricultural statistics appears to be erroneous. For example, every five years grass <br />pasture acreage increased by an average of 200 percent, followed by an average 200 percent decrease the <br />following year. The grass pasture acreage fluxuations likely were due to combining CABS: "hay other" <br />category with irrigated grass pasture NABS crop type on a five-year basis. These factors were taken into <br />consideration when this information was compared to irrigated acreage classification results. <br />Page 8 of 59 tij,Rareradde ~eshn~Pegy, ~os~ <br />