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ODl536 32 .8--8 WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK Common Step 8 - Normalize and display the representative station hydrograph s. Oisplay the daily mean hydrograph data from the representative gage station and divide the ordinate (CFS) axis by OB for the station. Note: The addition of the station flow-duratjon hydrograph may be useful to demonstrate the relative magnitude of bankfull discharge and the dampened nature of the daily mean hydrograph. Common Step 9 _ Identify on the representative gage station long term daily mean hydrograph the start of the snowmelt season. From the long term daily mean hydrograph of the representative gage station displayed in Common Step 8, identify the date during the snowmelt season which corresponds to the occurrence, for at least 24-hours, of mean annual discharge ("day 1"). The beginning of the rising lil{lb of the maintenance flow hydrograph begins after a user defined lapse of time following day 1. This is subject to user discretion. The objective is to identify the average date of occurrence of peak flow and to approximately align the maintenance flow hydrograph peak with this date. Common Step 10 - Using the representative station normalized flow-duration curve, plot the maintenance flow hydrograph. With the completion of the calculations of the required flow components, their duration, and the determination of the "Day 1" Index point, the scheduling of rising, bankfull, and recession flow components occurs using the displayed hydrograph(s) from Common Step 8. The flow rates for the individual rising or step-up segments and their related durations are plotted as the beginning portion of the maintenance flow hydrograph. Following the last rising component step, the effective discharge is plotted with its related duration. Following the effective discharge component, a series of one-day recession flow segments are plotted. The recession flow segments each have 1 day durations at flow rates as commensurate with the flow rates of the rising steps as practicable. The remaining portion of the maintenance flow hydrograph consists of the baseflow and low-flow rates and durations. These flows (QLl and QL2) may be plotted, with user discretion, on each side of the rise-bankfull-recession components (see Appendix B, exhibit 4). Common Step 11 - Flow, duration, and timing for maintenance flow components at the point of quantification. Using the ratios displayed in Common Step 2 calculate required flows by multiplying each ratio by the bankfull discharge calculated for each point of quantification. These flow values are required for the durations calculated in Common Steps 2 and 3 on the dates described in Common Step 10.