Chris Gargan and Joel Irving alongside a large IWS screen.
How IWS Builds Customized Fish Screens
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alifornia-based International Water Screens (IWS) creates custom-designed fish screens for irrigation districts and other canal managers. Its products meet the specific needs irrigation districts have for approach velocity, opening size, and flow level. IWS has sold its products both in the United States and in New Zealand. In this interview, Rich Gargan, owner of IWS, speaks with Irrigation Leader Editor-in-Chief Kris Polly about how his company creates fish screens, from design to construction.
All our fish screens are self-cleaning. If you put a screen with 3/32-inch openings in the water, it will catch debris like moss, leaves, and sticks. If you let it accumulate, the debris will plug the screen. Once that happens, the throughput velocity increases to the point that fish will start to impinge on the screen. It has to be self-cleaning to avoid that from happening.
Kris Polly: Please tell us about your background and your company.
Rich Gargan: Close to 50. A lot of times, we build what we think is a traveling screen, and after we put it in, the customer says, “Oh, by the way, this needs to work as a fish screen.” Then we have to make small changes so that it can also serve that purpose.
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Kris Polly: What are the key design factors that irrigation districts or schemes should be aware of when creating a fish barrier? Rich Gargan: The approach velocity that is required by law at its location is number 1. The size of the opening required at its location is number 2. The amount of flow, whether measured
PHOTOS COURTESY OF RICH GARGAN.
Rich Gargan: I’ve been in the screening industry for about 32–33 years now. Fish screens became popular around the early 1990s with the emergence of the environmental movement. We also manufacture traveling screens, which are designed with only debris removal in mind. We design our fish screens with different plastics and customize the size of the openings depending on the client’s requirements. Each fish screen is designed for a specific location.
Kris Polly: How many fish barriers or fish screens do you think you’ve designed and built?
