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<br />Background <br /> <br />f\) <br />r,) The Colorado River Salinity Control Act calls for the Secretary of <br />CO Agriculture to "provide continuing technical assistance for irrigation <br />~) water management as well as monitoring and evaluation of changes in <br />salt contribution to the Colorado River to determine program <br />effectiveness." The Natural Resources Conservation Service, formerly <br />the Soil Conservation Service, has met this responsibility since the <br />inception of the program. In the Grand Valley project, NRCS has <br />collected eleven years of hydrosalinity data that supports program <br />effectiveness. Data has been collected from 191 monitoring sites on a <br />variety of soils, crops and irrigations systems that exist in the <br />project area. The resulting data, summarized below and with <br />attachments, identifies the effects of the program and it's usability to <br />establish priorities with program participants and other irrigators in <br />the Grand Valley. <br /> <br />Total irrigated acres in the Grand Valley: 57,000 Acres <br />Crops Monitored <br /> <br />'Crop Ac. in. GV % of Irr. Ac # of M&E sites % of M&E sites <br />Alfalfa 30,000 53% 63 33% <br />Corn 14,000 25% 46 24% <br />Sm. Grains 4,700 8% 26 14% <br />Beans 2,400 4% 9 5% <br />Orchards 2,300 4% 30 16% <br />Onions 1,000 2% 3 2% <br />Grapes 200 <1% 10, 5% <br /> <br />The above data shows that the hydrosalinity monitoring sites accurately <br />reflect the crops and the significance of crops grown in the project <br />area. The M&E sites also reflect 94% by acreage of the crops grown in <br />the project area. <br /> <br />Approximately 98% of the irrigation is surface irrigation, the remaining <br />2% consists of side-roll and microjet sprinkler systems. Monitoring was <br />conducted on 181 surface systems, or 95% of all sites over the eleven <br />'year monitoring period. <br /> <br />The monitoring data was used to develop the 1994 monitoring evaluation <br />report which revised salt load reduction goals for the project. <br />Briefly, the revised salt load reduction goals were changed based on the <br />effects of the project on deep percolation. The latest summary of <br />monitoring data continues to support the 1994 report that deep <br />percolation is reduced by three inches with surface systems and six <br />inches with sprinkler and surface automated surge valve systems. This <br />information is displayed on the attached graphs. Additionally, the <br />following is deep percolation comparisons of irrigation systems, crop <br />rotation, and crops in the Grand Valley. Those comparisons are as <br />follows: <br /> <br />Chart 1. SYSTEM COMPARISON <br /> <br />This is a comparison of the most common "traditional unimproved systems' <br />and "improved systems" found in the Grand Valley. This gives a good <br />look at the "Trend" of deep percolation by system regardless of crop <br />grown. Deep percolation values used are the average of all sites for <br />that type of system over the eleven year period(1985 through 1995). <br />12 <br />