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Show PART II PRESENT STATUS OF IRRIGATION irrigation methods, depth of water application, adequacy of the irrigation system, and the skill of the irrigator. Because of the wide range of phys- ical factors, namely soils, topography, and climate, there is also a com- parable range of application efficiencies. Estimated field efficiencies attainable in the Upper Colorado Region for the various irrigation methods are as follows: level border 50-80 percent, graded border 60-75 percent, furrow ^5-70 percent, contour ditch 1+0-60 percent, corrugation k^-JO per- cent, and sprinkler 65-75 percent. Contour ditches in Wyoming demonstrate a common irrigation method used on sloping lands. Note the river bottom meadow lands in background where flood irrigation is practiced. Sixty-eight percent of the region's irrigated cropland is in grass hay and pasture. About 80 percent of these crops are produced in moun- tain meadows of Colorado and Wyoming, and most of the remainder (18 per- cent) is produced in the Uinta Basin and along the east slope of the Wasatch Range of Utah. Permanent pasture and native grass hay are the most common crops grown in high elevation, short-growing season areas. Water is usually diverted by temporary structures and is delivered by gravity canals and ditches to the fields where it is spread by small con- tour ditches by controlled or uncontrolled flooding. Some of these irri- gated areas receive natural overflow water during the period of high streamflow, which corresponds generally with the first part of the irri- gation season. In these areas where the growing season is short and the water supply limited, the water application efficiencies are low for the flooding and overflow methods of irrigating. It has not been practical 16 |