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<br />• 8,800 feet is about 24 inches with a water equivalent of about 6.8 <br />inches on or about April 1. Data for the period of record for this <br />station were utilized in a snowmelt flooding analysis for Ralston <br />Creek (see Appendix B-1). <br />3.3.3 Runoff Characteristics <br />The greatest volume of surface runoff in the Ral~.ton Creek <br />watershed commonly occurs from snowmelt. However, peak flows generally <br />result from late spring and summer thunderstorms. According to Jarrett <br />(Oral Communication, 1983), the most destructive flooding ~~n Ralston <br />Creek would result from intense rainfall associated with severe thunder- <br />storm activity. <br />Data on streamflow volume and treated Schwartzwalder Mine <br />water flow in Ralston Creek are available for calendar dears 1975 <br />through 1918. These flows, in acre-feet, are summarized by month and <br />• calendar year in the report "Surface Water Flows in Rals~;on Creek, <br />1975 Through 1978", prepared for the Cotter Corporation by Hazen Re- <br />search, Inc. (Golden, Colorado) in 1979. Collection of this volumetric <br />data continues. At present, however, no continuous-recorc data are <br />available for Ralston Creek suitable for determination of peak discharge <br />information. <br />Peak flood flow estimates for Ralston Creek are reported by the <br />Urban Drainage and Flood Control District in the "Major [irainageway <br />Planning, Phase B Master Plan" for Ralston and Leyden Creeks (1977). <br />These estimates have been designated and approved by the Colorado Water <br />Conservation Board. Because these peak flows are the result of the most <br />detailed study that has been done for Ralston Creek to date, and have <br />been approved by the agencies, they have been adopted as the basis for <br />use in this study and are further discussed in Section 5.2.1, <br />• <br />- 12 - <br />