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<br />00lGo9 <br /> <br />" . <br /> <br />32.3 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />to adjust its boundaries in response to changes in frequent flows. As a <br />result, it is usually impractical to measure channel characteristics at the <br />gage station in the literal sense. Therefore, make channel measurements <br />above or below the gaging site. <br /> <br />32.3 - Method A. Use Method A where stream cross-sectional area and water <br />surface slope can be measured at gaged sites and all points of <br />quantification. <br /> <br />S~~p 1 - Secure the following data from the representative gage station <br />a suitable gage stations. Some of these data will require collection <br />the field if unavailable from station records. <br /> <br />a. Mydraulic geometry and related discharge. <br /> <br />b. Stage-discharge relation. <br /> <br />c. Channel cross. sectional area at bankfull stage (and baseflow stage <br />for the representative station). <br /> <br />and <br />in <br /> <br />( <br />, <br /> <br />d. Water surface slope at bankfull stage. <br /> <br />e. Wetted perimeter, hydraulic radius, and roughness (if Manning's <br />equation is used to estimate discharge). <br /> <br />f. Field-41lE!asured bankfu1 discharge, if feasible. <br /> <br />Secure for the representative gage station the following: <br /> <br />a. Duration table of daily values summary for the period of record. <br />b. Mean annual discharge. <br />c. Daily mean hydrograph data for period of record. <br /> <br />Step 2 - Determine bankfull discharge and baseflow for the representative <br />gage station. Using either field measurements of discharge or hydraulic <br />geometry relations (or cross-sectional area data) with the stage-discharge <br />curve from the representative gage station, determine the discharge at the <br />bankfull (Qij) stage. Using depth ratios, stage, or cross sectional area <br />determine dlscharge at the basef10w (QLl) stage. (Note: Basef10w stage <br />is the water surface elevation associated with the discharge that just <br />fills the thalweg or inner berm channel.) <br /> <br />~ - Collect data at all suitable gage stations. Calculate or measure <br />~1 discharg~ as described in step 2. <br /> <br />Step 4 - Develop general relationship. From the data of the representative <br />and all suitable gage stations and using an appropriate statistical <br />technique, develop the relationship: <br /> <br />{ <br />\. <br /> <br />QB . kA~sY <br /> <br />ID No. 1 <br />9/10/85 <br />