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<br />Table 9.--Range. 1.n 6illed va.tu.e..6 06 hydttauLi.c cortduc;ti.v-Uy <br />60lL both IUUn6aU.--6-imulatOlL JtI./.Yl.6 and ob-6eJLved <br />iUUn.6aU.-JU.U'!066 event.; <br />[Results in inches per hour. Values in parentheses <br />indicate ranges not available.] <br /> <br />Plots <br /> <br />Source of data <br /> <br /> 1 2 3 4 <br />Simulator 1.1-1.5 1.1-1. 2 1.0-1.3 1. 0-1. 5 <br />(sunnner). <br />Simulator 0.5-0.65 (0.75) 0.65-1.0 (1. 3) <br />(fall). <br />Observed events 0.4-0.7 0.5-1.0 (1. 2) (1. 3) <br />'(sunnner). <br /> <br />HRUs (hydrologic-response units). Each HRU is considered to be homogeneous <br />with respect to the factors affecting runoff, such as slope, vegetation type, <br />and infiltration characteristics. Two levels of partitioning are available: <br />the first level considers the hydrologic characteristics just listed; the <br />second level describes the drainage network in terms of overland-flow plane <br />and channel segments, for the purpose of routing flow. <br /> <br />The drainage area of the North Fork watershed was partitioned into four <br />HRUs, based on vegetative cover, soil type, and slope (fig. 24). Areal <br />photographs, field reconnaissance, and a U.S. Geological Survey quadrangle <br />map (Bijou, Colorado) were used to delineate the area of each HRU. HRU 1 <br />is grass-covered, with gentle slopes and soils typical of those on plots 1 <br />and 2. HRU 2 is the same as 1, but is considerably steeper. HRU 3 is the <br />area with ponderosa pine and grass cover, has steep slopes with incised <br />channels, and has soils typical of those on plots 1 and 2. HRU 4 is <br />relatively steep and is mostly grass-covered; the soils are intermixed: <br />soils typical of plots 1, 2, and 3 are represented. Each HRU was assigned <br />parameter values derived from simulator plots. <br /> <br />The watershed then was partitioned into subbasins, and the area of each <br />HRU within each subbasin was determined (fig. 24). From this subbasin <br />delineation, a conceptual drainage network of channel segments and overland- <br />flow planes was developed (fig. 25). Each rectangle represents an overland- <br />flow plane, of HRU type 1, 2, 3, or 4, contributing to a channel segment. To <br />reduce the number of overland-flow plane segments required to conceptualize <br />the drainage network, the length, slope, roughness, and surface-retention <br />capacity were assigned representative values based on the four HRU types. <br /> <br />41 <br />