53:119 Hydrology
Problem #3
Ralston Creek Water Budget (Climatology)

The National Weather Service (NWS) uses 30-year averages to define climate "normals" (or the climatology).  Estimate the monthly and annual climatology of key hydrologic variables for the North Branch Ralston Creek (USGS Gage 05455000) watershed.  Use only the data for the 30-year period from 1952 through 1981 to compute average monthly and average annual values.
  1. Compute the average monthly precipitation (in inches) for each month for Iowa City.  The monthly precipitation data obtained from the National Climatic Data Center.
  2. Compute the average monthly discharge volume (in cfs-days) for each month for the North Branch Ralston Creek.  The monthly discharge volume were obtained from the U.S. Geological Survey.  (You might find the data easier to work with if you download it directly from the USGS web site.  Be sure to check the units).
  3. Compute the average monthly discharge (in inches) for each month for the North Branch Ralston Creek [e.g., volume/area].
  4. Plot the average monthly precipitation (in inches) and the average monthly discharge (in inches) versus month (one plot).
  5. Compute the average annual precipitation (in inches).
  6. Compute the average annual discharge (in inches).
  7. Compute the average annual evapotranspiration (in inches) using a long-term water budget..
  8. Compute the runoff coefficient (i.e., annual discharge as a fraction of precipitation) (in %).
Note that it is common in hydrology to consider the partitioning of precipitation (over long time scales) into (1) the portion that becomes discharge (or runoff), and (2) the portion returned to the atmosphere by evapotranspiration. Part (h) asks you to determine the percentage of precipitation that becomes discharge.

Last changed on 08/24/12 by aab.