53:078 Principles of Hydrology (Spring 2004)
Problem #4
Gage Catch Deficiency from NWS Quad Cities Web Site

Use the gage catch deficiency curves (Figure 4.16 from Handout) to correct the gage measurements (i.e., estimate the "true catch") for the Iowa City station.  Find the corrected precipitation for the days with precipitation in December 2003.  

To obtain the weather data for this period, go to the National Weather Service Quad Cities Climate page, then from the pull-down menus for the Month-to-Date Data Table (Preliminary F6 DATA) select <Iowa City, IA>< DEC>< 2003>.  The precipitation depth (water equivalent in inches) is shown in column 7 (labeled "wtr" --- the "T" stands for a trace, or less than 0.01 inches, which is negligible), and the average daily wind speed (in mph) is shown in column 10 (labeled "avg").  You can determine whether the precipitation was snow by looking at column 8 (but use the water equivalent in your calculation).  For the calculations, you may assume that (1) the gage is unshielded, and (2) all precipitation is in the form of rain if the snow (column 8) is a trace or zero, and all the precipitation is in the form of snow if the snow (column 8) is greater than a trace.  For each day with (non-zero) precipitation, compute the following:

  1. Gage catch deficiency (%)
  2. Corrected precipitation (in inches) (accounting for the gage catch deficiency)
(HINT: Be sure indicate days where the precipitation is rain, and days where the precipitation is snow).

For the month December 2003, compute:

  1. Uncorrected total monthly precipitation (in inches).
  2. Corrected total monthly precipitation (in inches).

Last changed on 02/03/04 by aab.