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. techniques used to predictdischargecharacteristicsofTuttleDrawandCalamityDrawinvolvedthe use of regression relationships determined from historical streamflow records in Western Colorado. Basin parameters and precipitation records were used to correlate discharge characteristics offour different regions of Western Colorado: l) Mountain; 2) Rio Grande: 3) Southwest and; 4) Northwest. Using the regression model for the southwestern region, the mean annual discharge and peak discharges from the 2-, 5-, 20-, 25-, 50-, 100- and 500-year recurrence intervals were predicted at two locations each in both Tuttle and Calamity draw. For both draws, discharge characteristics were calculated forthe entire drainage (atthe mouths), and atthe mostdownstream surface water monitoring site in each Draw (SW-N3, Tuttle Draw and SW-N 103, Calamity Draw, see Map 2.04.7- 1). See also Table 7-38, Volume B of New Horizon 1 Reclamation Plan. Streams -Flow This section presents discussions of flow data collected at surface water monitoring sites established atthe New Horizon 2 mining area. All historic data (priorto December, 1987) for each site has been compiled and is presented in Peabody Appendix 7-5. The reader should refer to Map . 2.04.7-1 to find stream monitoring site locations. Calamity Draw. Flow variability in Calamity Draw is artificially controlled by irrigation waterfor most of the year. From about mid-April torrid-October, the West Lateral irrigation ditch (managed by the CCC) is in continuous operation. Exact dates for turning this ditch on and off varies from year to year. Water from the West Lateral is also used primarily for irrigation and secondarily for maintaining water levels in stock ponds and domestic cisterns. Because of the operation of this ditch, the majority offlow in Calamity Draw is irrigation return water. Due to the relatively limited but heavily cultivated and developed watershed area in the upper portion of Calamity Draw, little supplemental flow from precipitation and snowmelt runoff occurs. Surface water monitoring Site SW-N101 was established in Calamity Draw above the eastern boundary ofthe New Horizon 2 Mining Area (see Map2.04.7-1). SW-N101 was monitored forflow since July of 1986, as part of the baseline monitoring program established for this mining area. Peabody Appendix 7-5 contains instantaneous discharge measurementcollected atthis site since 1986. During the irrigation season, measured discharge ranged from .605 in April up to 13.4 cfs (REVISED 6/28/01) 2.04.7-25