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<br />3~71 <br /> <br />of the year two crops are grown sequentially on the same acre of land, then that acre <br />is counted twice in reaching the total of 508,441 acres. <br /> <br />The Jensen/Walter Supplemental June 2003 report also indicated no change in the <br />distribution of crops among the major groups over the peliod li'OJn May 2000 through <br />April 2003 and that crop evapotranspiration has remained fairly stable. Within major <br />groups there have been some recent shifts between individual crops, most notably a small <br />decrease in alfalCa acreage and a small increase in wheat acreage. The shilis had no <br />sigmficant impact on crop ET (ET,), This finding was incorporated into this <br />deteImmation. <br /> <br />There is little or no variation among the technical reports submitted 10 Reclamation in the <br />amounts of crop acreage used in their analyses, since the primary data source used by all <br />technical experts is [(D crop reports. For instance, in the 2002 update to its 1997 report, <br />NRCE used annual crop acreages for the period 1989 to 1998 (NRCE 2002, Appendix <br />tic). Annual acreages during this timeframe for field crops varied between 364,000 acres <br />and 421,000 acres, acreages for garden crops varied between 88,000 acres in the late <br />] 990s and 125,000 acres in the early 1990s, and acreages for permanent crops varied <br />between 18,000 and 22,000 acres in recent years. Total crop acres have been decreasing <br />since 1998. <br /> <br />Crop evapotranspiration is the largest component of on-farm irrigation water <br />requirements for IID. In turn, crop acreage for each individual crop is one of the <br />important inputs into the models that calculate the amowlt of water required for crop <br />evapotranspiration (ET,). As such, it is a critical input into determining the amount of <br />water required for on-farm water use by the crops themselves. This determination relied <br />upon the 2000 to 2002 crop mixture, because this incorporated the most recent years and <br />thus reflects the current cropping trends actually used by the farmers to meet cun'ent <br />market demand for agricultural products. <br /> <br />FACTOR 7, TYPES OF IRRIGATION SYSTEMS IN USE <br /> <br />Part 417.3 identifies the types of irrigation systems in use as a factor to be analyzed. The <br />overwhelming majority ofthe crops grown in the Imperial Valley are irrigated by surface <br />(gravity) in'igation systems (NRCE 2002, p. 1l-14). Other irrigation methods in the <br />valley include spnnkler and drip irrigation systems, Sprinkler lITigation is being used by <br />farmers in lID for seed germination, crop establishment, land preparation purposes, and <br />occasionally for leaching. The use of drip irrigation depends on such factors as crop <br />type, water quality management, yield, and economic return (id., p, 11-14 to II-IS), In <br />2002 thef'e were approximately 12,000 acres irrigated by drip systems in IlD (IlD 2002 <br />Crop Report). Tllis is less than 3 percent of total irrigated acreage. <br /> <br />July 2, 2003 <br /> <br />20 <br /> <br />Detemlinations and ReconunendatlollS <br />For liD - Calendar Year 2003 <br />