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<br />0017J8 <br /> <br />36.2--13 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDaOOK <br /> <br />c. The channel maintenance flow hydrograph for the .point of <br />quantification is then determined. This hydrograph will have the same <br />shape of the hydrograph scheduled for the representative station as shown <br />in exhibit 4. In this example, the only difference in the maintenance <br />flow hydrograph for Gold Creek as compared to Gander Creek will be a <br />slight increase in the magnitude of discharge on the y-axis since Qa of <br />Gold Creek (185.8 cfs) is slightly greater than Qa of Gander Creek <br />(173 cfs). <br /> <br />STEP 4. Total Natural Water Yield for Gage Station (optional). <br /> <br />a. The worksheet (ex. 6) for estimating the total water yield, <br />represented by the area under the flow-duration curve may be prepared with <br />a set of constant values for columns 1 through 4. These values include <br />pre-selected percent time limits in column 1; the equivalent percent time <br />increment for these limits in column 2; the percent time increment <br />converted to .days duration in column 3; and in column 4 the percent time <br />value for the mid-ordinate point of the percent time increment from <br />column 2. <br /> <br />(' <br />\, <br /> <br />(1) From the flow-duration curve (ex. 2), read the Q/Qa ratio <br />values at the point on the y-axis corresponding to the mid-ordinate <br />percent time value. Record the ratio values in column 5. <br /> <br />'(2) Multiply the Q/Qa ratio values in column 5 by the Qa value <br />and record in column 6. <br /> <br />(3) Calculate a Time-Volume Coefficient (TVC) by multiplying the days <br />duration from column 3, the ratio value from column 5, and the constant <br />conversion factor, 1.9835 (column 3 x column 5 x 1.9835). Record the <br />result in column 7. <br /> <br />(4) Multiply the values in column 7 by Qa to produce AcFt volumes <br />related to the individual total water yield increments. Record the result <br />in column 8. <br /> <br />(5) Sum the values of column 7 (TVC) and column 8 (AcFt). The total <br />of column 8 becomes the estimate of total water yield. The total of the <br />individual TVC may be applied to the estimated QB value for an ungaged <br />drainage area to estimate the total water yield for that drainage area. <br /> <br />b. Alternatively, an estimate of total natural water yield may be <br />developed by taking the QA/Qa ratio for the representative station, <br />multiplied by Qa for the station of interest, multiplied by 1.9835, <br />multiplied by 3654ays. [For example, (QA/QB x Qa x 1.9835 x 365) _ <br />total natural wate~ yield when: QA/Qa is taken from the <br />representative station normalized flow-duration curve and Qa is <br />calculated for the point of quantification]. <br /> <br />1D No. 1 <br />9/10/85 <br />