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<br />" f'" r~; ,...-, <br />':"\)~i <br /> <br />Within the Purgatoire River reach below Trinidad Lake, <br />approximately 42,640 acres of cropland is currently being <br />irrigated. This cropland lies primarily within 2 hydrologic unit <br />areas (HUAl-the Apishapa, and the Purgatoire hydrologic units <br />(USGS HUA's 11020007, 11020010). In 1995 the Natural Resources <br />Conservation Service conducted an inventory of irrigation systems <br />as required as a part of the third RCA National Appraisal. Of <br />the total irrigated acres, 38,540 acres are planted to alfalfa or <br />alfalfa/grass; 3,400 acres planted to small grains/oats, and the <br />remaining 700 acres p~anted to row crops. The predominant row <br />crop is corn.. <br /> <br />The results of the analysis showed that for these two hydrologic <br />unit areas there were only two irrigation methods being used. <br />Approximately 24,590 acres are currently irrigated using graded <br />furrow/corrugation methods, while more than 42 percent of the <br />irrigated acreage (18,050 acres) is irrigated using contour ditch <br />and wild flooding. of particular note is that about 11.7 acre- <br />feet of water per acre is being applied seasonally to these <br />fields using contour ditch and wild flooding techniques. <br /> <br />Many of the irrigation systems have not had any improvements made <br />in the 80-year history of the systems and are considered to be <br />inadequate and in severe need of improvements. The field <br />application efficiencies were estimated to be as low as 28 <br />percent. <br /> <br />All of the improvements, if any, have been made in the Purgatoire <br />hydrologic unit. A few producers have started improving their <br />irrigation water delivery and application systems. Installation <br />of gated pipe, lined ditches, and underground pipe has increased <br />over the Past 4 years. Field application efficiencies of these <br />improved systems range from 40 to 4 percent, a very significant <br />increase as compared to the unimproved systems. <br /> <br />The RCA appraisal noted that irrigation-induced erosion and <br />sediment movement were significant. Of the total movement about <br />50 percent of the total lost from cultivated fields is being <br />deposited on-farm in ditches, ponds, and other fields: 10 percent <br />deposited in irrigation canals and drains, and 25 percent <br />deposited in water bodies. A significant portion (10%) of the <br />sediment deposition is occurring in existing wetlands. The <br />remaining 5 percent of the sediment deposition was found to be <br />occurring in culverts, ponds and other agricultural lands. <br /> <br />B. pUrPose <br /> <br />Based on the need for significant improvements in critical water <br />management practices a "scoping process" was developed to address <br />key issues and come to an understanding as to what the needs of <br />the "customer" really are. A formal scoping process was <br />conducted on February 12, 1996, with several representative <br />farmers from the hydrologic unit areas. Agency facilitation <br />included staff from the NRCS and the Colorado State University <br /> <br />oZ <br />