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<br />National Weather Service NOAA Atlas #2 "Precipitation-Frequency Atlas <br />of the Western United States" Volume III-Colorado, U.S. Department of <br />Commerce, NOAA, National Weather Service, Silver Springs, Maryland, <br />1973, which is hereby incorporated by reference into this Rule and <br />does not include later amendments to our editions of the incorporated <br />material; or other methods approved by the State Engineer, are used to <br />determine the lOO-year precipitation. When using precipitation data <br />for determining probable future water flows, the analysis shall <br />consider whether such precipitation occurred as rain or snow, and the <br />magnitude, duration and frequency of precipitation. <br /> <br />5.A.(5)(d)(I)(E) The National Weather Service, NOAA, <br />Atlas #2 "Precipitation-Frequency Atlas of the Western United States" <br />Volume III-Colorado, U.S. Department of Commerce, NOAA, National <br />Weather Service, Silver Springs, Maryland, 1973, is hereby incor- <br />porated by reference into this rule, and does not include later <br />amendments to, or editions of, the incorporated material, 1973, or <br />other documents approved by the State Engineer, may be used for <br />determining the lOO-year precipitation for calculating the lOO-year <br />flood. <br /> <br />Rule 5.A.(5)(d)(I)(F) Whenever a determination of the <br />50-year or 25-year flood is appropriate, the same principles of Rule <br />5.A. (5)(d) apply. <br /> <br />5.A.(5)(d)(II) Whenever a determination of probable future <br />surface water flows, or the probability of frequency of their <br />recurrence, at any place in Colorado is required by relation to a <br />longer period than that for which there is a reliable record of flows <br />as defined in (I) above (e.g., flows resulting from Probable Maximum <br />Precipitation), the determination shall be made by interpolation and <br />correlation of known records to the longer period by relating known <br />records of water basins as similar as reasonably possible to the place <br />of determination or basin under consideration, or by use of geologic <br />determinations, or determining Probable Maximum Precipitation by use <br />of other methods reasonably calculated to formulate an accurate <br />estimate of probable future flows or the probability of frequency of <br />their recurrence at the place of determination of such flows. The <br />following methods or other methods approved by the State Engineer, are <br />acceptable: <br /> <br />5.A,(5)(d)(II)(A) Site specific hydrometeorologic <br />analysis, following procedures used by the National Weather Service, <br />to transpose large historical storms to the drainage basin under con- <br />sideration to determine the Probable Maximum Precipitation. Snowmelt <br />conditions shall be considered as base flow when appropriate. <br /> <br />- 18 - <br />