High Head Dam Fish Passage: Does Dam Height Still Have to Be the Hard Problem?
Author : Whoosh h... | Published On : 20 Aug 2026
Dam height has been treated as a defining constraint in fish passage design for most of the field's history. The taller the dam, the harder the passage problem. Fish ladders, the default solution at smaller structures, become increasingly expensive and hydraulically demanding as height increases. At high dams, conventional ladders require enormous water diversions, complex civil engineering, and years of construction before a single fish passes through them.High head dam fish passage has a reputation as an intractable problem partly because the standard toolkit was genuinely limited at extreme heights.
The Importance of Fish Elevators
Fish elevators can handle higher structures but introduce mechanical complexity, failure risk, and throughput limitations. Trap and haul programs sidestep the structure entirely but require road access, crew presence, and vehicle infrastructure that remote mountain sites often can't support.
The underlying assumption in all these approaches is that fish passage height scales linearly with difficulty. More height means more water diversion, more civil structure, more cost. Whooshh Innovations built the PassagePortal and MigratorTube transport system on a different assumption: that height is not the limiting
variable when the transport mechanism doesn't depend on water.
Pneumatic transport using approximately 1 PSI of differential air pressure moves fish through flexible MigratorTubes at 25 feet per second. The tubes can run up to 1,000 feet in standard configuration, with Booster Stations extending beyond that for taller structures.
A low head dam fish passage solution and a high head application use the same underlying technology. The only difference is tube length and the number of booster stations in the run. Dam height stops being a fundamentally different category of problem.
What Does This Mean for High Head Facilities?
It means several things practically. First, the capital cost of passage at a tall dam no longer scales with height the way it does for conventional ladders. A MigratorTube installation at a 300-foot dam doesn't require 300 feet of stepped concrete pools, each needing its own water management and maintenance regime. The tube runs up the embankment or structure face, fish travel through it in seconds, and the infrastructure footprint is a fraction of what a ladder would require.
Second, the water diversion question becomes much simpler. Conventional high head ladders divert substantial water from the headpond to maintain the stepped gradient fish need to swim through. At high dams generating significant hydropower, that diversion represents real revenue loss. The PassagePortal system's attraction flow draws from the tailrace, not the headpond, and the fish transport itself uses air pressure rather than water volume. Up to 10% more of the river's flow can remain in the power generation system.
How Does the Big Bar Landslide Case Illustrate This?
In 2019, a massive landslide on the Fraser River in British Columbia blocked salmon migration entirely. The blockage was in remote terrain with no roads and no existing infrastructure. Whooshh deployed a PassagePortal system to that site within three months, operational without road access or grid power, and passed thousands of Chinook Salmon past the obstruction during the remaining migration window.
That deployment demonstrated something important: the technology's height-independence and remote deployability aren't theoretical advantages. They've been tested under real emergency conditions at a site that no conventional passage infrastructure could have reached in the same timeframe.
What Does This Mean for Licensing and Compliance?
High head dam operators facing FERC relicensing reviews or equivalent regulatory processes in Canada and Europe have historically listed fish passage as one of the most costly compliance obligations at high structures. The combination of reduced installation cost, lower operating cost, and the real-time FishL Recognition monitoring data that Whooshh systems generate changes that calculation.
The full range of Whooshh fish passage systems covers both high and low head applications. Whooshh Innovations is actively working with dam operators across a range of structure heights and site conditions. Read the published blog Unlocking Hidden Hydropower for a broader look at the hydropower and passage relationship. For a site-specific conversation, contact the Whooshh team directly.
