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-24 ~ U~~1 1\ tl <br />Surface Water <br />The area of the Eagle No. 5 and No. 9, and the Trapper Mines is drained by the <br />Yampa River, and the Williams Fork River, both perennial rivers which ,)oin <br />within the permit boundary. The Williams Fork River is a mayor tributary to <br />the Yampa. It flows in a northerly direction in the permit boundary to the <br />confluence with the Yampa River. The Yampa River flows in a southwesterly <br />direction across the permit boundary. <br />The area of the Sugarloaf Mine is drained by Lay Creek and one unnamed, <br />ephemeral to intermittent tributary of the Yampa River. Lay Creek is a <br />perennial stream which has its confluence with the Yampa River 2 miles east of <br />Maybell gaging station. The confluence of the unnamed tributary with the <br />Yampa River is located about 3 miles south of the Sugarloaf Mine's permit area. <br />Flow in the Yampa River depends primarily on snowmelt from the winter snowpack <br />on the high mountain slopes surrounding the drainage basin. The lower <br />intermittent and ephemeral drainages produce only a small part of <br />the total water yield of the basin (Colorado Water Conservation Board, 1969). <br />Hydrographs of flows from the Yampa River drainage basin demonstrates the <br />importance of snowmelt runoff to water yield. Figure 6 is a hydrograph of the <br />mean monthly discharge of the Yampa River at Maybell (drainage area - 1,430 <br />square miles), from 1916 to 1965. About 64X of the flow occurs in May and <br />June with up to 84% occurring from April to July at selected gaging stations <br />within the drainage basin (Steele, et al, 1979). Minimum flows generally <br />occur from August through February. Irons, et al. (1965) reported that <br />summertime flows in streams of the basin from July through October generally <br />include a large component of ground water discharge. <br />Extremes recorded at the Maybell gaging station are a maximum flow of 17,900 <br />cfs on May 19, 1917 and a minimum of 2.0 cfs on July 77-19, 1934. Annual <br />variation in yield may also be great. Historical annual yield has varied from <br />345,000 acre-feet in 1977 to 2,135,000 acre-feet for the Yampa River in 1917. <br />Average annual yield amounts to 1,116,000 acre-feet. <br />The Williams Fork River is a mayor tributary to the Yampa River and enters the <br />Yampa River within the permit area of the Eagle Mines. It drains <br />approximately 350 mil, or 70X, of the Yampa River Valley and shows many of <br />the same characteristics as the Yampa River, except that the Williams Fork is <br />more dependent on snowmelt and there is less ground water discharge to sustain <br />the flows of the river during low flow periods. <br />In addition to yield, water quality also varies seasonally. Total suspended <br />sediment loads are at a maximum during peak flows associated with spring <br />runoff. Steele et al., (7979) reports that up to 90X of the annual sediment <br />load of the Yampa River at the Maybell station is discharged during the period <br />of snowmelt runoff. Figures 7, B, and 9, present the graphs of suspended <br />sediment loads versus discharge for the Hayden and Craig sites on the Yampa <br />and the mouth of the Williams Fork rivers respectively. Total suspended <br />sediment loads increase with increased discharges (flows) in the rivers. <br />Dissolved solids loads show an inverse relationship with stream discharges. <br />High quality snowmelt runoff contains relatively low levels of total dissolved <br />solids (TDS). <br />