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5 <br />• Regional Irrigation Evaluation <br />In the newly issued Office of Surface Mining (OSM) guidelines <br />for alluvial valley floor determination, a number of indices <br />are suggested for evaluation of regional irrigation <br />practices. These include drainage basin area, maximum height <br />of irrigated acreage above water source, and successful <br />irrigation in hydrologically similar basins. Table 5 <br />summarizes the drainage area and maximum elevation for the <br />four draws associated with the Kerr Mine area. <br /> Comparison of the characteristics of the four draws <br /> associated with the Kerr mine area with the characteristics <br /> of the apparently successful Canadian Basin irrigation <br /> schemes located in similarly sized basins suggests that none <br /> of the four draws have characteristics consistent with <br /> successful irrigation schemes. Specifically, apparenCly <br />• successful Canadian Basin irrigation schemes located in <br /> similarly sized basins to the four draws (i.e., basins rang- <br /> ing from 2,140 acres to 6,470 acres) are oriented southwest, <br /> and have maximum basin elevations from 10,880 feet to 12,560 <br /> feet. Bolton, Williams, Bush and Sudduth Draws, on the other <br /> hand, are oriented northeast and have maximum basin eleva- <br /> Cions extending approximately 8,500 feet in all but Bo1Con <br /> Draw, which extends 9,050 feet. The potential for snow pack <br /> accumulation and resultant runoff (water supply) is much <br /> greater in all of the apparently successful Canadian Basin <br /> irrigation schemes than in the four draws associated with Che <br /> Kerr mine area because of the higher basin elevations. In <br /> addition, the estimated mean annual precipitation received by <br /> the apparently successful Canadian Basin irrigation schemes, <br /> which do not have the Canadian River for their source, is <br /> greater than 25 inches in their upper reaches, while the <br /> estimated mean annual precipitation received by the four <br /> draws associaCed with the Kerr mine area ranges from only 92 <br /> inches to 16 inches. <br />Leonard Rice Consulting Waler Engineers. Inc. <br />