Stiff Diagrams

 

 

Stiff Diagram

Stiff diagrams are graphical presentations of the cation and anion content of water presented in milliequivalents per liter. More information on the application of Stiff diagrams can be found in the USGS Water Supply Paper 2254, Study and Interpretation of the Chemical Characteristics of Water available at http://pubs.usgs.gov/wsp/wsp2254/ .    

Stiff diagrams may be generated in EnviroInsite as either georeferenced plots (small diagrams with a leader to the well location) or as full page Stiff diagrams.  In the full page Stiff diagram plot, the diagrams are lined up vertically along the centerline of the page.  In order to create a full page Stiff diagram, select Window - New - Stiff Diagrams from a plan view map.  Then select Plot - Stiff Diagrams.

By convention, cations are plotted on the left side of the Stiff Diagram and anions on the right. The Equivalent Weight field in the constituents table is used to convert between the measured mass concentration and the concentration in equivalents or milliequivalents per liter.  The Equivalent Weight field should be entered as positive for cations and negative for anions.  If the concentration values are entered as milligrams per liter or parts per million then the following values in the Equivalent Weight field will convert the concentrations to meq per liter.

Click here to view a training video on generation of stiff diagrams in EnviroInsite.

Cation / Anion

Equivalent Weight

Na

22.9898

K

39.098

Ca

20.04

Mg

12.1525

Fe (II)

27.97

Fe (III)

18.65

Mn

27.469

Cl

-35.453

HCO3

-61.016

SO4

-48.03

CO3

-30.004

NO3

-62.04

NH4

-18.039

PO4

-31.66

 

Query

Select Ions

The anions and cations to be plotted in the Stiff Diagram are selected in the Select Ions tab of the Stiff Diagram dialog box.  Each line on the Stiff Diagram can represent a single ion or the sum of two ions.  Leave the second ion blank to plot a single ion or leave both ions blank to not plot a particular line.

 

In addition to the query options, the Stiff diagram dialog box offers the following options to customize the appearance of the plot:

Options Tab

Labels

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