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for each discharge characteristic based on the southwestern region's regression model <br />(Kircher, et al., 1985). Table 7-39 presents the results of the calculations for each <br />drainage. <br />From Table 7-39, it is evident that Calamity Draw has an annual mean discharge of about <br />one half that predicted for Tuttle Draw. This relationship generally holds true for the <br />remainder of the calculated discharge characteristics. <br />Streams - Flow. The following sections present discussions of flow data collected at <br />surface water monitoring sites established at both the Nucla Mine and Nucla East mining <br />area. The discussions are grouped according to the drainage in which the sites have been <br />located. For instance, discussion of flow data for Sites SW-N1 and SW-N3 will be found <br />under the section titled "Tuttle Draw". All historic data (prior to December, 1987) for <br />each site has been compiled and is presented in Appendix 7-5. The reader should refer to <br />Exhibit 7-1 to find stream monitoring site locations. <br />Tuttle Draw. As is characteristic of all of the surface water sites at both the Nucla <br />Mine and the Nucla East mining area, the flow regime in Tuttle Draw is artifically <br />• controlled by irrigation practices for most of the year. From about mid-April through <br />mid-October, the Second Park lateral irrigation ditch (managed by the Colorado Cooperative <br />Company) is in continuous operation. However, exact dates for turning the ditch on and <br />off vary from year to year. During this period, water from the ditch is primarily used <br />for irrigation and secondarily for maintaining water levels in stock ponds and domestic <br />cisterns. Between mid-October and mid-April, the ditch is turned on occasionally in order <br />to maintain levels in stock ponds and cisterns. As a consequence of the operation of this <br />ditch, the majority of flow in Tuttle Draw is irrigation return flow except for occasional <br />supplemental flow from precipitation and snowmelt runoff events. <br />Surface water monitoring Site SW-N1 is located in Tuttle Draw upstream of the Nucla Mine <br />permit boundary. SW-N1 has been monitored for flow routinely since April of 1980. Table <br />7-40 presents means and ranges of monitored instantaneous discharge at both Sites SW-N1 <br />and SW-N3. Table 7-40 shows that flow measured at SW-N1 varies from zero up to 11.6 cfs. <br />During the irrigation season (approximately mid-April through mid-October), the means of <br />measured discharge range between .149 and 2.94 cfs, with high flows measured from .275 in <br />April up to 11.6 cfs in September. During the non-irrigation season, (mid-October through <br />• mid-April) flow ranges from .034 up to 1.03 cfs. <br />7-112 Revised 04/11/BB <br />