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<br />32.6--2 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />set and recurrence interval most nearly approximating the <br />bankfull stage discharge of the representative gage station <br />should be the chosen alternative. <br /> <br />A. Steo 1. <br /> <br />1. Secure the fOllowing data from the representative gage <br />station. <br /> <br />a. Duration table of daily values summary. <br />b. Mean annual discharge. <br />c. Daily mean hydrograph data for the period of record. <br /> <br />2. From the representative and all suitable gage stations <br />secure the following data. <br /> <br />a. Drainage area of watershed above gage. <br />b. Area-weighted mean elevation of watershed above gage. <br />c. Other watershed characteristics if appropriate. <br />d. Log-Pearson type III 1.5 years return interval peak flow <br />(daily mean flow and/or other return interval if appropriate). <br />e. Log-Pearson type III 1.5 years return interval, 7-day <br />low flow (or use the locally calculated return interval and <br />duration which best correlates to the flow which fills the inner <br />berm, or thalweg channel). <br /> <br />B. Step 2. Develop general ~elationship. Regress the log- <br />Pearson type III 1.5 years return interval discharge (Q ) <br />against drainage area for the representative and all su~table <br />gage stations using watersheds in similar area-weighted mean <br />elevation zones to develop a relationship of the following form. <br /> <br />where, <br />Q <br />f(DA~ <br /> <br />Qs = f(DA) <br /> <br />= log-Pearson 1.5 years return interval flow and <br />= some functional relationship of drainage area, <br /> <br />Note: Develop this relationship for as many elevation zones <br />as chosen. Alternatively, if the data are not stratified by <br />elevation zones, the user may develop a relationship of the <br />following form. <br /> <br />where, E = elevation. <br /> <br />QB = f(DA,E) <br /> <br />*-FSH 4/89 AMEND 3-* <br />