The Duration analysis allows the user to show the percent of time that a hydrologic variable is expected to equal or exceed value(s) of interest. Many different types of regular interval data (i.e 1HOUR, 1DAY, etc) can be analyzed including flow, stage, precipitation, and wind speed (amongst others).

Create a new Duration Analysis

  • Click Analysis | New | Duration to create a new Duration analysis.
  • Name the analysis "Palisades_Duration".
  • Select the Palisades pool elevation data set within the Data Set drop down menu.

The data set will be named "Palisades Pool Elevation".

  • On the General tab:
    • Select both the Start Date and End Date checkboxes. Enter a Start Date of 01Oct1959 and an End Date of 30Sep2017.
    • Select User-Defined within the Duration period drop down menu and enter the following seasons:
      • 01Jan through 31Mar
      • 01Apr through 30Apr
      • 01May through 31May
      • 01Jun through 30Jun
      • 01Jul through 31Jul
      • 01Aug through 31Dec
  • Leave all other options unchanged. The General tab should appear similar to the figure below.

Compute and Visualize the Results

  • Click the Compute button at the bottom of the Duration analysis editor. A window informing you that the computations are complete should appear. Click OK to close this window.
  • Click the Plot Duration Curve at the bottom of the Duration analysis editor to view the results. A window similar to the figure below should appear.

  • Notice that there are six computed curves and six interpolated curves within this window. Click on each data set in the legend to better identify which data set is associated with each legend item in the plot.
  • When you are done, close the plot and move to the Results tab. Take note of the tabular information that is contained within this tab.
  • Click the View Report button to open the report.
  • Within the report window, take note of the expanded information that can only be found within the report file. When you are finished scrolling through the report, close the window by clicking the "X" button in the upper right corner of the window.

Question 4: How many valid values were included within the 01May – 31May duration curve computations? How many years' worth of data does this represent?

1798 values were included within the 01May – 31May duration curve computations.  This represents approximately 61 years’ worth of data (1957 to 2018).


  • Click OK to close the Duration analysis editor.
  • Click the Save button (  ) to save the study.

Continue to Task 5. Create and Parameterize a Volume Frequency Analysis.