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. 0.4 mi Ie downstream from the U.S. Highway 50 bridge. There are 7 other stations on the main stem and 20 stations located on tributaries up- stream from John Martin Dam, some of which were establ ished prior to 1900. The average annual flow of the Arkansas River at Las Animas for the period 1939-59 is 185,300 acre-feet. The annual flow varied from a minimum of 20,340 acre-feet in 1959 to a maximum of 1,022,000 in 1942. The records are publ ished in U.S. Geological Water Supply Papers. The highest known peak discharge at Las Animas is 187,000 c.f.s., which occurred on June 4, 1921. 18. U. S. Highway 50 and the Arkansas Val ley Branch I ine of the AT~SF Rai Iway System cross the Arkansas River north of Las Animas. The U.S. Highway 50 bridge is a through-truss bridge, about 760 feet long with a 15-foot roadway. The Colorado State Department of Highways considers this bridge obsolete from a traffic standpoint and has sched- uled its replacement in the near future. The rai Iroad bridge, 858 feet long, consists of a central deck girder section with trestle sections at either end. 19. CLIMATOLOGY.- The cl imate of the Arkansas River watershed in Colorado varies widely between the plains and the high mountainous regions. Precipitation averages from 12 inches annually in some locations to rates of 20 to 40 inches over I imited areas on the crests of the mountain ranges. The annual precipitation is quite evenly dis- tributed throughout the year in the higher elevations but a large percentage of the total is in the form of snow and some stations have reported snowfal I during al I 12 months of the year. Most of the annual precipitation over the plains occurs from Apri I through August. Las Animas experiences extreme temperature variations. The maximum and minimum temperatures in 72 years of record are 1140 and -320. The mean monthly temperature varies from 30.90 in January to 79.60 in July and the mean annual temperature is 55.00. The average length of the growing season in the vicinity of Las Animas is 155 days, which occurs between May and October. The average annual relative humidity is 52 percent, varying from 38 percent at 5 p.m. to 70 percent at 5 a.m., as recorded at Pueblo. The average evaporation for the period Apri I through October is 65 inches at John Martin Dam. Wind data recorded at Pueblo indicate the prevai I ing direction to be from the west at an average velocity of 8 mi les per hour. The maximum speed recorded was 80 m.p.h. in January 1950. 20. The precipitation records for Las Animas, dating back to 1867, are the most complete and extensive records of any in the Arkansas Val ley. The annual precipitation has varied from a minimum of 2.79 inches in 1894 to a maximum of 21.39 inches in 1923, averaging 12.35 inches per year for the period of record. The month of July has the highest average monthly rainfal I (2.09 inches); but the greatest amount ever recorded during anyone month is 7.54 inches, which occurred during Apri I 1900. The maximum dai Iy rainfall of 3.60 inches occurred in July 1958. Snowfall at Las Animas averages 20.1 inches, annually. 8