Why we are sold on the Floating Streambed – by Bruce Kania

The latest innovation to come out of Floating Island International is our floating streambed. We’ve been testing versions of this innovation for seven years now. Before I get into the results, let me tell you the back-story.

Early on in our research efforts, some twelve years ago, a study being run at the Montana Center for Biofilm Engineering in Bozeman found that nutrient uptake increased with circulation. Reduction of nutrients is key to water quality. So the next question was, “what’s the upper limit for circulation?” In a follow-on test, in the lab, the scientists could not find an upper limit. The more circulation…the greater the nutrient uptake into biofilm. Biofilm is the primary element of nature’s scrubber system…wetlands. This group of scientists found that surface area and circulation were the two primary variables that limit biofilm-generating microbes; in other words, that limit nature’s “wetland effect”.

Based on these findings, here at Shepherd we asked the question…how do you maximize for surface area and circulation? Conventional BioHaven floating islands with gravity-based circulation and wind/wave action were developing a history of excellent performance. But we continued to notice that the very best results corresponded with the greatest amount of circulation. At times we would see results that were ten-fold higher than our modeling projections.  So we explored small-bubble, high-pressure vertical aeration, horizontal aeration via an impeller pump, low pressure/high volume pump technology, and finally, air lift pump systems that use low pressure to move water by displacing it with air.

This work led to our floating streambed system (formerly known as Leviathan), run by an air lift pump. It is approximately 600% more efficient than the next best low pressure/high volume pump system. At Shepherd we have two of these streambed units, powered by three-horsepower air blowers, on either end of Fish Fry Lake. These streambeds are the reason Fish Fry lake’s water clarity has gone from 14 inches to as much as 19 feet, and why nitrogen that enters Fish Fry in unpredictable volumes, intermittently, is taken to non-detect in the lake’s outflow, and ultimately why Fish Fry Lake, at 28 pounds of wild fish harvest per acre foot, with no feeding, is currently the most productive wild fishery of over 50 acre feet in Montana.

What does it mean to be such a productive fishery? It means that kids catch fish…about one every two minutes. Many have never fished before. It means that we keep two drum scalers on hand and operational so folks can process fish quickly and easily, and go home with meals of delicious fish fillets. It means that the water of Fish Fry Lake is inviting, and a pleasure to snorkel or dive…certainly when compared to its initial status, when swimming was impossible due to the mats of algae. It means that dragon flies and damsel flies are almost a constant. And correspondingly, mosquitoes are hard to find near the water. It means that other life forms, like freshwater sponge, are now occurring in the lake, and expanding biodiversity. Freshwater sponge is also a filter feeder, so it’s also helping the lake transition to even higher water quality. It means that life forms that only occur in healthy, well-oxygenated water can now happen in the lake, where before they were disallowed. The reverse is true too. Life forms that vector with impaired water, including mosquitoes and the midge that spreads Blue Tongue, if present at all are only here in minuscule numbers.

Other key features include:

  1. Maximal nutrient cycling
  2. Potential spawning habitat for riverine species like trout (we successfully hatched Yellowstone Cutthroat in an early embodiment of streambed)
  3. Maximal water filtration
  4. Maximal water aeration, as cooler water which re-oxygenates more readily than warm water is perched at the surface for an extended period
  5. Maximizes for circulation and corresponding performance enhancement for conventional biohavens
  6. Very quiet, inexpensive year round operation

There’s more. In fact, my sense is that putting such a system into a static waterway expands potential for biodiversity because now those species that require at least some circulation have this optional feature on offer, as my British wife Anne would say. There are many life forms that occur in riverine habitat, but which don’t occur in static waterways. And the more biodiverse your waterway is, the more resilient it is to the nutrient and other contaminant issues fresh water faces today.

For more information on the floating streambed system call us at 1-406-373-5200.