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Going with the Flow: Oceanit Study Aims to Improve Water Quality at Kawai Nui Marsh

Posted July 1, 2015 in Environmental Engineering, In the News

A transfer experiment at Kawai Nui Marsh aims to restore a wetland habitat for native water bird species and improve water quality.

Located near Kailua on the windward side of Oahu, Kawai Nui Marsh is the largest fresh water marsh in the Hawaiian Islands. Serving as an important flood control basin, a levee was constructed to enhance its flood storage capacity. While the flood control levee protects the residents during floods, it has cut off the natural flow of water from Kawai Nui Marsh to Kawai Nui Stream, creating an area of stagnant water.

A planning study, being conducted by the Department of Land and Natural Resources and Oceanit, uses four 6-inch siphons to pull water from the marsh into the stream to measure and stimulate water flow without adversely impacting the existing flood control structure. The study aims to improve the wetland habitat for native waterbird species; water quality, hydrologic conditions, and water movement; and tidal exchange with the ocean at the stream mouth. As Oceanit scientist Robert Bourke explains, “Stagnant water is not good for the fish, not good for the birds, not good for the people who live next to the stream and have to smell it.” Approximately 2 cubic feet of water per second flow from the marsh into the stream. The siphon system will help raise the water surface elevation of the stream by approximately one inch. “It's important that we are able to regulate and control the water level of wetlands, so we don't inundate the chicks and the eggs before they’ve hatched,” says Bourke.

Continuing through the summer, the study will help to determine the best feasible method to restore water flow. Watch the KITV4 News report on the siphon project here. For additional information, contact Oceanit by telephone at (808) 531-3017 or via e-mail at