Program Description

WTRBLN is a computer program that calculates water balance based on the basis of long-term average monthly precipitation, potential evapotranspiration and vegetation characteristics, according to the method of Thornthwaite and Matter. The program is based on the work of Donker 1987. The paper includes an appendix that provides the source code that was written in Basic 3.0.

During my PhD years I was asked if I could rewrite the code using a more modern language. At that time I decided to write it in matlab and I made also a simple GUI for that. To my surprise I found many years later that this small program has been used by many students at the university, therefore I decided to give to this small program a place on my page.

How to use

The program launches with the following command

and the GUI shows up as show below

The usage is quite simple. The first text box expects any random text that describes the study. This text is printed in the input file and it is not used during calculation. The first group of data ask the user to enter 12 values (one for each month) for Precipitation, Evapotranspiration, Direct Runoff and Crop Coefficients. The program to run requires also two scalar values i) Average Monthly Runoff and water Capacity for rootzone. Because the program always prints the data to a file, a filename is required. Note the filename has to have an extension such as *.txt, *.dat, etc otherwise it will be without extension. Last there are two boolean inputs. If Use Inputs from file is true the program ignores any user input in any of the fields and attempts to reads the data from the file that is provided. The file must be located in the currently active matlab workspace. The Generate input file only simply prints the data of the gui to a file without running the model. The button of course triggers any of the above actions. After the model calculation there will be a variable named out in the matlab workspace which contains the results of the model and a figure that shows the results of the model in a way similar to the plots of the paper of Donker 1987. The figure below shows the result of the first example of the paper.

Download

You can download the code from this link

The program consist of two matlab scripts *.m files and a *.fig file, therefore after downloading the code you can run it directly from matlab. Together with the source files I have uploaded two examples of input files for each of the examples of the paper.

References

Donker N.H.W., (1987), WTRBLN: a computer program to calculate water balance. Computers & Geosciences, 13(2), 95-122, doi:10.1016/0098-3004(87)90002-1.

 Other resources

This is a small list of works that the WTRBLN program used. They are all written in Greek with English abstracts.

• Gavallas, Valileios I. (2009), Εκτίμηση υδατικού ισοζυγίου και προσομοίωση υπογείου παράκτιου υδροφορέα λεκάνης Γαδουρά στη Νήσο Ρόδο
• Strantzalis, Kostantinos N. (2008), Προσδιορισμός υδάτινου ισοζυγίου υπόγειου παράκτιου υδροφορέα της Ν. Θήρας υπο την επίδραση έντονων κλιματικών αλλαγών
  
• Evagorou, Evagoras S. (2012), Εκτίμηση Ιδατικού ισοζυγίου και προσομοίωση του υπόγειου παράκτιου υδροφορέα Ακρωτηρίου