Task 4. Fit the Log Pearson Type III Distribution to Each Annual Maximum Series

All-Season

Now that you have extracted mixed population, summer-only, and winter-only annual maximum series, you will create a Bulletin 17 analysis to fit the Log Pearson Type III analytical distribution to each annual maximum series.

• Select Analysis | New | Bulletin 17 Flow Frequency.
• Name the new analysis “Mixed_B17C” and add an adequate description.
• Select the Mixed Peaks data set.
• Ensure the 17C EMA method is selected within the Method for Computing Statistics and Confidence Limits panel.
  • This will automatically select other features including the Multiple Grubbs-Beck low outlier test and Hirsch/Stedinger Plotting Positions.
  • The General tab should resemble the following figure.

• Move to the EMA Data.
• Ensure that the Flow Ranges table contains a low and high value for every single year in the analysis period. The completed EMA Data tab should resemble the following figure.

• Click Compute.
• Click Plot Curve. This will result in the computed curve, 5- and 95-percent confidence limits, and observed events being plotted.  The plot should resemble the following figure.

• Close the computed curve window.
• Move to the Tabular Results tab.
• Note the computed curve, 5-, and 95-percent confidence limits for all of the desired frequency ordinates, the moments/parameters of the Log Pearson Type III fit to the data, and other data related to the analysis.

Summer Season

• Repeat the previous steps to fit an LPIII distribution to the summer season annual maximum series, creating a new Bulletin 17 analysis for just the summer peaks.

Winter Season

• Repeat the previous steps to fit an LPIII distribution to the winter season annual maximum series, creating a new Bulletin 17 analysis for just the winter peaks.

Question 1:  Fill out the following table with the LPIII parameters for each analysis.

Continue to Task 5. Create a Mixed Population Analysis Using the Summer and Winter B17C Results.