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WSPC07406
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Last modified
1/26/2010 12:10:50 PM
Creation date
10/9/2006 6:27:27 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8062
Description
Federal Water Rights - Colorado Litigation - National Forest ISF Claims - Technical Sutdies
State
CO
Basin
Statewide
Date
8/28/1987
Author
Unknown
Title
Technical Studies - Water Information Management System Handbook - Chapter 30 - Procedure for Quantifying Channel Maintenance Flows
Water Supply Pro - Doc Type
Report/Study
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<br />001595 <br /> <br />32.8--7 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />.- <br /> <br />Common Step 5 - Survey channel cross-section to measure channel area <br />assoclated with potential vegetation encroachment. <br /> <br />The area to be considered for vegetation encroachment prevention flows <br />generally lies between the top of the inner berm and the start of the <br />Channel banks. Survey the channel cross-sectional area below the elevation <br />defined by the start of channel banks. These measurements are made at the <br />point of quantification or at the representative gage station (if <br />sufficiently similar to allow extrapolation). <br /> <br />Common Step 6 - Determination of vegetation encroachment prevention flows <br />(QLV)' <br /> <br />The discharge needed to prevent vegetation encroachment is calculated using <br />the cross sectional area measurments and a stage-discharge relationship, if <br />available at the quantification point, or the Manning and continuity <br />equations. A~ alternative appro.ach utilizes the ratio of cross-sectional <br />areas, ie., AV/Ab . QLV/QB and solving for QLY.* <br /> <br />* Note: Use "b" as defined in a relation of the form Q . KAb derived <br />from gage station records or local data. For method D assume "b" . 1. <br /> <br />If vegetation encroachment potential at the point of quantification is <br />similar to that of the representative gage station, a ratio for vegetation <br />encroachment prevention flow can be developed at the representative gage <br />station using stage-discharge or hydraulic geometry relationships and <br />applied directly at the point of quantification. <br /> <br />Common Step 7 - Calculate the duration of QLY' <br /> <br />The calculated discharge must next be converted to a ratio to determine <br />it's duration. The discharge is divided by QB and the resulting ratio is <br />identified as a point on the flow-duration curve. The duration (percent of <br />time equaled or exceeded) may then be noted, converted to days and <br />described as an increment as in Common Step 3. (If the ratio of areas <br />approach (p. 91) is used it is clear, assuming the equality, that the area <br />ratio is the same as the one derived by dividing the calculated flow by <br />QB. ) <br /> <br />The calculated duration must next be adjusted to both the duration and <br />timing of the growing season. This season is the period during which the <br />vegetation encroachment potential is greatest, and the susceptible portions <br />of the channel area identified in Common Step 5 are not inundated. If this <br />season is greater than the calculated duration of inundation, the <br />difference in days is added directly to the discharge requirements <br />described in Common Steps 2 and 3. <br /> <br />ID No. 3 <br />8/20/87 <br />
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