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Thornthwaite and Mather
Water Balance
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Easy-to-Use Analitical Software

Two fully interactive versions of the water budget that estimate monthly potential and actual evapotranspiration, directly from C. W. Thornthwaite and J. R. Mather, 1957. The Water Balance, Publications in Climatology, Vol. X, No. 3, Drexel Institute of Technology, Centerton, NJ.

This is easy-to-use software that calculates potential and predicted evapotranspiration (and runoff) based on mean monthly precipitation, temperature, and latitude. In other words, potential ET is determined form the energy and amount of water available. It works in any DOS environment (DOS-Prompt in WINDOWS from 98 to WINDOWS XP Professional 2002. The program's algorithms are created from and conform to Thornthwaite and Mather's original tables as revised in 1957. Also, see my linked "Atrticle Reprints" page (or below!) to obtain a copy of a Technical Note published in JAWRA on some confusion on using T&M and why it is much better than has been often mentioned in other articles (all documented). The article as submitted for publication is included with the software.

Full reference is provided in the accompanying brochure, which also contains theory, operations, limitations, demonstration data, and sample output. The program is supplied on a 3” CD unless specified otherwise by email. (The entire program including accompanying instructions is only 1.4 megabytes.)

EACH VERSION:

  • Requires mean or actual monthly temperature, precipitation and, if desired, runoff;
  • Provides screen or print options;
  • Produces mean annual tabular water budget organized by months, climatogram, and comparison of predicted and actual runoff, if entered;
  • Functions in a DOS or WINDOWS 9x or Windows XP Professional environment, and;
  • Comes mailed postage paid on a 3" CD with a four-page explanatory brochure and test data/output..

RECENT RESEARCH PAPER:

  • "Revisiting the Thornthwaite and Mather Water Balance." The Thornthwaite and Mather method of calculating the monthly pattern of annual the water balance has been criticized, but is also misunderstood. Download a free copy of my recent paper published in the Journal of the American Water Resources Association to set the record straight. Click here. For a free download of the Adobe file.

ADDITIONAL NOTES:

  • Both editions now operate in WINDOWS XP Professional (although I don't know about 2007) as well as WINDOWS 97 or 98. You can also re-start your computer in DOS MODE, by entering the subdirectory where the software is located and entering the word SOLVE.
  • It is easiest to right click on the SOLVE.EXE file and send an icon to the desktop. Then, whenever you wish to start the software, click on the icon. Remember to exit the SOLVE software with the F4 key and a "Y" (as instructed).
  • The software also operates in any DOS environment (on 286, 386, or 486 PCs) or, in WINDOWS 9x, where you can use PRINT SCREEN or screen capture software to store the printed output as a file that can then be pasted into a WORD document, for example, which also enables making use of the software's color graphics).
  • I recently discovered a simple, rapid, and inexpensive way to get the tabular and graffic output: use your digital camera to photograph -- without the flash -- the screen. When shown on the screen from the image, the data looks a bit rough, but on printing it out (e.g., as a figure in a MS WORD file) it is quite legible.

Click here to buy the
School Version: $30
Use your credit card.
It is easy, fast, safe, and secure.

This version was designed for ninth grade earth science classes. It features monthly tabular and graphed outputs of the annual water budget, and graphic comparison of measured and predicted runoff. Output may be viewed on the screen and/or printed. This version will be especially useful for ninth-grade earth science, general or natural science, biology, geography, or for meteorology or climatology teachers.

Sad note: the software apparently does not work in a VISTA environment.

Click here to buy the
 Professional Version: $100
Use your credit card.
It is easy, fast, safe, and secure.

This version is the same as the school version, but includes the opportunity to perform sensitivity analyses by making multiple runs once the input data are supplied. Successive “what-if?” runs may be made with (1) different soil storage capacity, (2) latitude (effecting a "translocation" of a sloping watershed at some aspect to an equivalent latitude), (3) elevation (reflecting varying snowmelt runoff models), and (4) significant hydrological watershed characteristics, land use considerations, and unusual hydrological factors. This will be of particular value to those working on water balance research projects as well as consultants in wetland creation and management, and sanitary landfill calculations.
© Peter E. Black Updated 1/9/10