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Q: I don’t know if or when my stream was altered. Can I still use IHA?
A: Yes. You can use IHA in the "single period" mode to create graphs that portray the values of each IHA parameter over the period of record. Those graphs may reveal substantial hydrologic changes beginning at some point in the record. This observation may help you to identify a perturbation that began at that time. Once you've identified the onset of an important perturbation, you can test the "pre" versus "post" impact period to further assess the magnitude of the perturbation.

Q: How has IHA been applied?
A: See the IHA Application Database and scientific papers for information on how the IHA has been used in support of planning, management and research. If you would like to include information about a project you've completed, please contact us.

Q: Can IHA calculate environmental flows?
A: No. IHA can be used to support the determination of environmental flow needs, but it does not generate recommendations. Determining environmental flow needs is inherently an interdisciplinary process, and integrates information about the hydrology, morphology, biology, and other aspects of a water body. First, you need to gain an understanding of which flow components are important for keeping your ecosystem healthy. IHA helps you understand how much those flows have been altered. Ecologists, water managers, and other stakeholders can use this information to decide on an acceptable amount of flow alteration for different times of the year and for different years – that is, the necessary environmental flow regime.

Q: Where can I obtain data for IHA?
A: IHA is a flexible program that can accept data in different forms. See Section 1.4 in the User's Manual. The U.S. Geological Survey's National Water Information System is a great resource for data.

Q: Can I use IHA for commercial purposes?
A: No. IHA is freely licensed for non-commercial purposes, but commercial use is prohibited unless written permission is obtained from The Nature Conservancy.

Q: I’m having trouble with a .csv file. What can I do?
A: Try opening the file with a text editor, like Windows Notepad, and resaving it.

Q: The batch processing function is crashing IHA. What can I do?
A: Try setting up the batch run, but before running it, close and restart IHA.

Q: I’m having trouble with an analysis that compares two datasets when using metric flow units. The results seem incorrect. Is there a bug? What’s going on?
A: There is a known issue with metric flow units and the analysis that compares two datasets. It appears that IHA automatically reads input units as cfs when comparing two datasets, even when the data units are defined as cms.
Here’s one way to work around the issue: in a spreadsheet, convert cms data to cfs, then create a new IHA project and define flow units as cfs. Import the converted data into the new project and proceed with the analysis. Results will be in units of cfs, but can be post-processed to metric if needed.
Additional Resources
Q: Is there training for IHA?
A: Yes. Online training is available in English and Spanish. In addition, onsite trainings are offered periodically at various locations. See the training page for announcements.
Q: I've signed up for the online training and tried to open content but nothing happens.
A: Check the settings of your web browser to make sure that pop-ups are allowed.



 Contact Us

If you have questions or comments regarding IHA, please contact James Limbrunner.