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<br />" <br /> <br />. <br /> <br />002544 <br /> <br />. <br /> <br />2.1.4.2 Surface Water Hydrology <br /> <br />The Arkansas River originates along the Continental Divide in the Rocky Mountains west of <br />Pueblo, Colorado. Mountain elevations can be greater than 14,000 feet msl, where perpetual <br />snowfields and springs feed the river. The main channel of the river flows south and eastward <br />through mountainous terrain and canyons into Pueblo Dam and Reservoir. Pueblo Dam is the <br />first major impoundment on the river, over 100 miles from the headwaters. Weather conditions <br />in the area vary greatly throughout the year. Precipitation within the entire basin ranges from 10 <br />to 40 inches. At higher elevations, much of the precipitation comes in the form of winter snows. <br />More than 80 percent of the annual precipitation in the study area comes in the form of summer <br />thunderstorms. The maximum rainfall months are May, June, and July (FEMA, 1986). Annual <br />average maximum and minimum temperatures are 680 F to 370 F, respectively (FEMA, 1986). <br /> <br />Flow data were obtained from four gaging stations near the study area, three of which are still <br />operable. The most upstream of the operating gages is maintained by the State of Colorado and <br />located 2,000 feet below the dam, called the Above Pueblo Gage (1D#07099400). This gage <br />began operation on October I, 1965, and is still active. The gage was moved 730 feet upstream <br />in 1975 when the dam came online (Flory, 1999). The post-I975 data represent releases from <br />the dam. The longest period of record in the study area comes from the inactive Near Pueblo <br />gage (1D#07099500) that was located near City Park and Lake Joy. This USGS gage operated <br />between 1894 and 1975 and its data represent pre-darn conditions. The Pueblo at Moffat Street <br />gage (1D#07099970) is located at the downstream end of the Reach 2. This gage carne online in <br />1989 and has since operated. The fourth gaging station in the study area is located on Fountain <br />Creek (ID#071 06500), and has been operated continuously since 1922, with two exceptions: the <br />gage was not operated between September 1925 and October 1940 and between September 1965 <br />and February 1971. This gage is located upstream of the confluence between Fountain Creek <br />and the Arkansas River and not affected by the installation of the dam. The published mean <br />daily flows through water year 1998 for all the study area gages are available online from the <br />USGS website. The 1999 provisional data were obtained from the USGS office in Pueblo. <br /> <br />The mean daily flows were used to compute average monthly flows (Table 2-11). In general, <br />releases from the dam are much lower in the winter than in the summer months with the lowest <br />sustained flows in January, averaging 138 cfs. In contrast, sustained releases from the first of <br />May through August average over 1,000 cfs for each month. <br /> <br />Arkansos RIver Fi~h~f1l.'s Habn:J.! Restoration, Pueblo, COIOTJdo <br />Fm:J.l Ecosystem ReslOr:.Jtlon Report Jnd Environment:J.1 Assessmen[ <br />11-32 <br /> <br />ChapleT II. Environmental Setting <br />September 200 I <br />