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•~ 2.1.2 Seasonal Precipitation <br />The average annual total precipitation for the proposed mine plan area, using <br />44 years of National Oceanic and Atmospheric Administration (NOAH) data for <br />Craig, Colorado, is 13.56 inches (34.44 cm). Martin (1980) states the U.S. <br />Weather Bureau has calculated a standard deviation of 3.5 inches. <br />Total annual precipitation has varied from a low of 7.43 inches (18.87 cm) in <br />1958 to a high of 20.83 inches (52.91 cm) in 1945. This is a range of from 55 <br />percent to 155 percent of [he long term average for the area. Monthly precip- <br />itation totals vary significantly from year to year as well. The annual dis- <br />tribution of precipitation is nearly uniform with approximately half occurring <br />from October through April (Woodward-Thorfinnson, 1974). Annual and monthly <br />precipitation totals from 1936 through 1979 are presented in Tab Le 2.1-4. In <br />27 percent of these years, Craig received 12 inches or less annually (Martin, <br />1980). <br />• The greatest total monthly precipitation occurred in October, 1941, and again <br />in June, 1945, when 4.55 inches (11.56 cm) were recorded a[ the Craig National <br />Weather Service (NWS) station. The least total monthly precipitation occurred <br />in October, 1952, when no moisture was recorded. This almost happened again <br />in May, 1969, when only 0.01 inch (<0.03 cm) was recorded and in May, 1974, <br />when just a trace of moisture was measured at the NWS station (Table 2.1-4 ). <br />The greatest daily (24 hour) precipitation event took place on August 7, 1970, <br />when 1.96 inches (4.98 cm) were recorded (Tables 2.1-5 and 2.1-6). <br />Using NOAA criteria for determining "dry months" during the pas[ 44 years <br />(based on [he frequency of receiving less than 0.25 inch) June and September <br />are the two "driest" months. <br />• <br />2-9 <br />