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Environment

"Tube fishways" could safely lift fish up and over dams

By Ben Coxworth
December 22, 2020
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Prof. Bill Peirson, with a fish about to make a trip up a tube fishway
UNSW
The team's small-scale tube fishway
UNSW
Prof. Bill Peirson, with a fish about to make a trip up a tube fishway
UNSW

Dams pose a great obstacle to fish migrating up rivers, potentially keeping them from breeding, thus leading to a decline in wild stocks. Australian scientists are on the case, though, with a possible solution known as the "tube fishway."

First conceived by the University of New South Wales' Assoc. Prof. John Harris, each tube fishway consists of … well, a long tube that stretches vertically from the water at the bottom of a dam, on its downstream side, up to the water on the other side of the dam, at the top.

Due to the pressure difference between the water at the upper end of the tube (behind the dam) and the lower end of the tube (below the dam), a hydrodynamic pumping system is produced. Stated more simply, a surge effect occurs, propelling water – and fish – up the tube.

Curious fish below the dam enter a funnel-shaped enclosure attached to the bottom of the tube, and are subsequently drawn up it and shot out of the top end, behind the dam. They can then continue on their migration up the river.

The whole process takes just a few seconds. What's more, air bubbles within the tube water help keep the fish oxygenated, plus they protect the animals against sudden changes in water pressure.

The team's small-scale tube fishway
UNSW

In a small-scale experiment, a 90-mm-wide (3.5-in) tube fishway was used to transport Australian bass from one tank to another, up an 8-meter (26-ft) elevation. And it is believed that the system should work on a much larger scale.

"Our numerical modeling work shows that this system will work reliably for pipes at least one meter [3.3 ft] in diameter, lifting fish more than 100 m [328 ft] vertically," says Prof. Bill Peirson, who is leading the project along with Dr. Stefan Felder. "This is potentially a game changer in the ecological management of large dams."

The scientists are now hoping to install an experimental tube fishway on the Marsden Street Weir, in the Australian city of Parramatta in the Greater Western Sydney region. They are also looking into ways of helping fish travel downstream over high dams and weirs, without being injured.

The testing rig can be seen in use, in the video below.

Source: UNSW

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EnvironmentUniversity of New South WalesFishConservationEcologyNew Atlas Audio
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Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.
8 comments
Daishi
Aww, I wanted to see the fish en route inside the tube.
Nobody
So this looks like a jet pump which forces the water up the smaller tube. Hopefully, the fish can stand the 14.7 psi pressure for every 34 feet of lift. So for a single stage 328 foot lift, at the bottom the fish will suddenly be subject to about 140 psi as they are sucked into the lift pipe and just as suddenly the pressure drops as they are discharged at the top. Am I missing something here???? Unless it is done in small steps, it sounds pretty traumatic for the fish.
WonkeyDonkey
Disappointing they didn't include a demonstration of a fish in transit. Proof of the pudding and all that. I imagine having a transparent tube would aid in research to count the number of fish (and leaves) traveling up the pipe, and also be a bit of a tourist attraction.
WonkeyDonkey
@Nobody - they were talking about the aeration effect protecting the fish from pressure differentials. I know a bit about aeration and cavitation from boating, but admittedly this is beyond my ken.
Nobody
@WonkeyDonkey, regardless of the aeration it still will require a lot of pressure to get to the top. Ski jumpers often practice by landing in an aerated pool where the expanding bubbles cushion their landing. That's a different application. As an old boater I am very familiar with jack plates and propeller cavitation. I don't think that applies here.
Greg Jeffcoat
Sablefish live between near shore and almost 9000’ deep. Most commercial harvest off the west coast US is from depths up to 3000’. That’s About 100 atmospheres, 1469 psi. They lack an air bladder, hence no inflation at 1 atmosphere. They are known to be returned to the sea and caught again months or years later. This fish tube technology should have minimal effects on the fishes’ viability. Ever see a remote mountain lake stocked with fish from a helicopter? They are dropped from the sky and have a high survival rate. Fish are tough critters, and tasty too.
McDesign
Hmm - I'm not getting how the pressure differential is generated.
Expanded Viewpoint
McDesign, everything below, must support everything which is above it. In what we call the air column, the air below is supporting the air above it. In the water column, the water below is supporting the water which is above. In a building, the first floor is supporting all of the floors that are above it. All of those are examples of Delta P, or pressure differential. There are pumps called hydraulic ram pumps, which use the energy of falling water to compress air which then pushes water uphill. You can find videos on YT that show how they work.

Randy
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