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<br />station record shall be deemed reliable if made by the State of <br />Colorado or United States as part of a regular program of either of <br />these entities, except as to any part of such records the State <br />Engineer shall have designated as being unreliable on the basis of <br />facts so showing. <br /> <br />5.A.(5)(d)(I)(B) Whenever a determination of a IOO-year <br />flood is required at a place other than the location of a reliable <br />stream gaging station, the determination of probable runoff at such <br />other place shall be made by relating the probable future runoff at <br />that place to the recorded runoff at a comparable gaging station or <br />gaging stations by the interpolation of reasonable hydrologic, <br />geologic, and natural vegetative factors. Unless clearly unrelated, <br />the factors of the comparison shall include, but not BE limited to, <br />the following elements or characteristics: <br /> <br />1. The water basin contributing to the probable <br />future flow at the place where probable future runoff is to be <br />determined, considering: basin size; the altitude or altitudes of the <br />basin; various soil permeabilities; the various vegetative covers; and <br />the aspect of the comparable basins; <br /> <br />2. The known runoff as determined by reliable <br />stream gaging stations using interpolations when necessary from <br />comparable gaging stations and relating interpolations to the <br />characteristics of the basin measured by the comparable gaging <br />stations as related to the basin of runoff being determined; and <br /> <br />3. The slope or slopes of the terrain whose sur- <br />face runoff contributes to the surface water flows at the place at <br />which a determination of probable future surface water flows is <br />required. <br /> <br />5.A.(5)(d)(I)(C) When using the gaging station records <br />as described above, calculations shall be based on procedures outlined <br />in the "United States Water Resources Council, "Guidel ines for <br />Determining Flood Flow Frequencies," Bulletin #I7B of the Hydrology <br />Subcommittee, Revised Edition, Interagency Advisory Committee on Water <br />Data, U.S, Department of the Interior, Geological Survey, Office of <br />Water Data Coordination, Reston, Virginia, 22092, March 1982, which is <br />hereby incorporated by reference into this rule, and does not include <br />later amendments to, or editions of, the incorporated material, or <br />other methods as approved by the State Engineer. <br /> <br />5.A.(5)(d)(I)(D) Historical precipitation data of the <br />National Weather Service may be used for determining probable future <br />water flows, provided applicable stochastic procedures outlined in the <br /> <br />- 17 - <br />