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Units Definitions for HydroCAD 6.0-7.1

This document describes the procedure for customizing the units for HydroCAD 6.0 to 7.1.  This procedure is not required for HydroCAD 8.0 and later, which allow individual parameters to be easily modified within each HydroCAD project.  Details here.

Creating a Custom Units Definition

To adjust the units with HydroCAD 7.1 and earlier, you must create a custom units definition file, as described below.

Warning: Custom unit definitions are a complex topic, and are recommended only for skilled users when no other alternatives exist. Errors in the units definitions can cause hard-to-detect errors in data entry or reporting! Before attempting to create custom units, contact HydroCAD support to be sure this solution is necessary for your application.  You should also consider using a newer version of HydroCAD that allows individual units to be easily customized within each project.

1) To create custom units you must create a new units definition file. This is best done by making a copy of one of the standard definition files. These files are called English.hcu and Metric.hcu, and reside in your HydroCAD program folder, which is normally C:\ProgramFiles\HydroCAD.  If you have trouble locating the files, use the Windows search capability to find the files.  You can also view a sample file here.

2) Select the file best suited to your needs, and open the file with any text editor, such as Windows NotePad.  When the file is open use File|SaveAs to immediately copy the file to a new name, such as MyEnglish.hcu.  This is essential to avoid changes to the original file.  When saving the file, be sure to include the .hcu extension.

3) Now follow the instructions and examples in the units file to modify the desired units definition(s).  Some commonly used custom units are shown below.  When done, close and save the new file.

4) To use the new units definition, open the applicable project in HydroCAD and select the new units file on the Settings|Units screen.  If you want to open the project on another HydroCAD system, be sure to supply your custom units file along with the project file.

Commonly Used Custom Units

Depending on your needs, you might use one or more of the following lines in your custom units definition:

To reduce the displayed flow values from 2 decimal places to 1 decimal place:

Flow1= 999999.9 0 cfs cfs 1 flow   reports only

To round the CN values to 1 decimal place instead of the nearest whole value:

CN= 100.1 1 . . 1 none

To allow exfiltration rates above 100 inches per hour:

ExfilVel=999.999 .001 in/hr in/hr 12*3600 velocity  exfiltration velocity

When using these examples, find the line that begins with the same name (e.g. Flow1) and replace the entire line in the file with the text shown above.  To ensure accuracy, use copy-and-paste to transfer the text.  Be careful not to disturb any other lines in the file.

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