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• The average annual flow of the White River near the lease area was estimated through the use of a flow <br />duration curve developed for the station identified as the White River above Rangely, Colorado. (USGS <br />station No. 09306300), located about 4.7 miles downstream from the confluence of Scullion Gulch and the <br />White River. Flow characteristics at this station are presumably indicative of the flow adjacent to the lease <br />area. The flow duration curve, as described by Searcy (1959), combines the flow characteristics of a <br />stream throughout the range of observed discharges into one curve and can be defined as a cumulative <br />frequency curve that shows the percent of time during which specific discharges were equalled or <br />exceeded during a given period. Although it does not show the chronological sequence of these flows, it <br />can be used to determine several hydrologic characteristics of a watershed, including the mean annual <br />flow. <br />The long-term flow duration curve of the White River above Rangely, Colorado was derived from short-term <br />records (since October 1972) using the index station method of Searcy (1959). According to this method, <br />flow duration curves are prepared for the period of record at the short-term station and the corresponding <br />period of record at a representative long-term (index) station (in this case, White River near Meeker, <br />Colorado -USGS Station No. 09304500). The discharges at selected percent-duration points on the <br />duration curve of the short-term station are then plotted on logarithmic paper against the discharges for the <br />same percent duration points from the duration curve of the long-term station. The relation between <br />discharges at the two stations for the short concurrent period is assumed to represent the long-term <br />• relation. Following the construction of the long-term (period of record) flow duration curve for the index <br />station, the flow available a given percent of time at the long-term station can be used to enter the curve of <br />relation (based on the shorter period of record) to obtain the adjusted (to long-term) flow available the same <br />percent of time at the short-term station. <br />Figure II.C-6 gives the flow duration curves of the White River above Rangely, Colorado and the White <br />River near Meeker, Colorado for the period of October 1973 through September 1978. The curve of <br />relation is plotted in Figure II.C-7. The long-term flow duration curve of the White River above Rangely, <br />Colorado (Figure II.C-8) was developed based on this curve of relation and the long-term flow duration <br />curve of the index station (White River near Meeker, Colorado). Note that the two long-term duration <br />curves have a similar shape and magnitude at flows above the 19 percent-duration point. This indicates <br />that high flows are primarily controlled by upper basin conditions (i.e., snowmelt from points above Meeker). <br />Although the shape remains the same, the magnitude begins to vary between the two stations at <br />percent-duration points greater than 19. <br />• Permit Renewal #3 (Rev. 8/99) II.C-12 <br />