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Introduction
Geert van Wirdum is one of the initiators of “Ecohydrology” in The Netherlands. Geert has developed several techniques for field measurements and data-analysis for ecohydrological research. His methods are applied by Deltares as well as by research institutes and universities in the rest of the world. One of his mostly used data-visualisation techniques is the so called ‘Van Wirdum-diagram’. This diagram shows the chemical similarity of a water sample to atmocline water (rainwater), thalassocline water (seawater) and lithocline water (calcium rich, fresh groundwater).
In a Van Wirdum's diagram, the ionic ratio (IR) is plotted against the electric conductivity (EC), where:
IR = [Ca2+] / ([Ca2+] + [Cl-]).
IR = Ionic ratio (-)
Ca2+ = Calcium concentration (mmol/L)
Cl- = Chloride concentration (mmol/L)
The scientific background on this “Van Wirdum diagram” is available through Geert van Wirdums PhD-thesis (Van Wirdum, 1990), which can be acquired by internet (http://www.scribd.com/doc/51589352/Vegetation-and-hydrology-of-floating-rich-fens). Figure 1 is an example of a ‘Van Wirdum-diagram’. These diagrams are regularly used by scientific institutes, universities, and ecohydrological consultants. The example comes from a study on flexible water level management (STOWA, Hoofdrapport Flexibel peilbeheer, 2012).
Van Wirdum diagram
We have programmed the framework of the typical ‘Van Wirdum-diagram’ in R. R is a free open source software program used for data processing and visualization and for statistical analysis. R is used throughout the world and has gathered a large community of users.
Acquiring R
For those who did not acquire R yet, have a look at the website http://www.r-project.org/ and download R at http://cran.xl-mirror.nl/ (for Dutch users).
In addition, we advice to install Rstudio (http://www.rstudio.com/ide/). Rstudio is a free enhanced graphical interface for R.
Function “vanwirdum”
This text needs to be copy-pasted into R. Notice that for direct usage of the vanwirdum function in R you need to have access to internet.
Using the van wirdum function without internet is possible but you need to download this file and replace the following.
If you are in need of help you can access these helpfiles.
Example
For an easy example you can use the RHdata or another dataset containing the date of measurement, EC (measured at 25 degrees Celsius) and IR (ionic ratio in %).
For some nice ideas about the use of this function we rever to the examples file.
Expert use
For more experienced R users and for further options for the use of the function we refer to the advanced file. Next to advanced examples it also includes the set up of the VanWirdum function and helpfiles prepared for use in R as a package.
