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The engineer in me wonders if there’s some way we can have dams and make salmon happy. Can we have a small stream that goes around the dam for example? The sa

The engineer in me wonders if there’s some way we can have dams and make salmon happy. Can we have a small stream that goes around the dam for example? The salmon ladders In Seattle seem pretty popular with the salmon. Can we not build something like that?

kibwen 4y ago
Plenty of dams do have fish ladders, although Wikipedia suggests that they're not perfect: https://en.wikipedia.org/wiki/Fish_ladder#Effectiveness https://en.wikipedia.org/wiki/Fish_ladder#Effectiveness
- wongarsu 4y ago
  They frequently suffer from misaligned incentives, with damns mostly being judged by the existence of a fish ladder, not its effectiveness. And while a stronger current helps fish find the way, that's water that's "lost" for the dam operator.
bombcar 4y ago
You can do it - but for the big dams it’s too long/tall. Arguably you could instead of damming a river divert a portion of it upstream into a new valley for a lake, leaving the old river alone.
froj 4y ago
There's this super over-engineered fully automatic fish elevator to go up a 20m tall weir [1] (pdf and German warning). Interestingly, there is no safe way for the fish to go back down, yet. [1] https://www.bkw.ch/fileadmin/bt3_news/MyConvento/2021/10/06/4336893/211006_MM_Inbetriebnahme_Fischlift_Wasserkraftwerk_Muehleberg_DE.pdf https://www.bkw.ch/fileadmin/bt3_news/MyConvento/2021/10/06/...
jasonwatkinspdx 4y ago
Most of the big damns up here in the PNW already have fish ladders. They help but they only partly mitigate the issue. There's a pretty crazy company developing this system that actually shoots fish up the damn like those pneumatic canisters bank drive throughs use (or used?). I just remember seeing a video about it but don't know anything more.
AdamN 4y ago
The other problem is the fish need to go downriver too. The dam extracts energy from the water flow and slows down the river - making it difficult for newly hatched salmon to even get to the ocean in the first place. The dams simply need to be removed, starting with the ones that offer minimal value in other dimensions (electricity, water supply, navigable waters, recreation, etc...) until eventually the vast majority are gone and only a few are left to protect important infrastructure that cannot feasibly be moved.

kibwen 4y ago

Plenty of dams do have fish ladders, although Wikipedia suggests that they're not perfect: https://en.wikipedia.org/wiki/Fish_ladder#Effectiveness https://en.wikipedia.org/wiki/Fish_ladder#Effectiveness

wongarsu 4y ago
They frequently suffer from misaligned incentives, with damns mostly being judged by the existence of a fish ladder, not its effectiveness. And while a stronger current helps fish find the way, that's water that's "lost" for the dam operator.

bombcar 4y ago

You can do it - but for the big dams it’s too long/tall. Arguably you could instead of damming a river divert a portion of it upstream into a new valley for a lake, leaving the old river alone.

froj 4y ago

There's this super over-engineered fully automatic fish elevator to go up a 20m tall weir [1] (pdf and German warning). Interestingly, there is no safe way for the fish to go back down, yet. [1] https://www.bkw.ch/fileadmin/bt3_news/MyConvento/2021/10/06/4336893/211006_MM_Inbetriebnahme_Fischlift_Wasserkraftwerk_Muehleberg_DE.pdf https://www.bkw.ch/fileadmin/bt3_news/MyConvento/2021/10/06/...

jasonwatkinspdx 4y ago

Most of the big damns up here in the PNW already have fish ladders. They help but they only partly mitigate the issue. There's a pretty crazy company developing this system that actually shoots fish up the damn like those pneumatic canisters bank drive throughs use (or used?). I just remember seeing a video about it but don't know anything more.

AdamN 4y ago

The other problem is the fish need to go downriver too. The dam extracts energy from the water flow and slows down the river - making it difficult for newly hatched salmon to even get to the ocean in the first place. The dams simply need to be removed, starting with the ones that offer minimal value in other dimensions (electricity, water supply, navigable waters, recreation, etc...) until eventually the vast majority are gone and only a few are left to protect important infrastructure that cannot feasibly be moved.