I mean, for those who care about California

Various reasons:
1. Because that would damage the local ecosystem a lot
2. That pipeline would be extremely long
3. It would only push the problem to Washington - the river is already being used
4. It would be so ludicrously expensive - Up to $13 million a mile for regular oil lines, but about 25 pipelines, so the eventual cost per mile would be over $300 million per mile and about 300 miles of pipe makes it around $90 billion, which is in the same price range as California High speed rail, and if funded federally, costs each taxpayer $270

Thanks for your reply! I appreciate your willingness to engage me on this topic.

I can't claim to know anything about relevant costs, but why would it require 25 lines? I didn't mean to divert the entire river, just a portion of the excess flow that currently drains into the Pacific. A pipeline would doubtless cause damage to the stretch between the river and I-5, but could then be run 100 yards off 1-5 roughly 600 miles to Lake Shasta, California's largest reservoir.

It would be expensive for sure, and at the end of the day any positive integer is too much for politicians and their constituents to willingly agree to. But in light of the inexorable aridification of California and corresponding annual outbreak of wildfires, it seems like the most sensible solution (band-aid).

The original cost I stated was for a standard oil pipeline, however, one might need significantly more capacity if transporting water, so I estimated a factor of 25

I do not know much about these things, but it seems to me that desalination would be the way to go in this case, and, correct me if I'm wrong, for fire fighting purposes, salt water could still be used.
Desalination is a tried and tested way of getting water in Israel, and other countries buy it from them because it's the only way for them. I think desalination would be a safer bet.

Ah, a cost factor of 25, that makes sense. It would certainly factor in budget overruns...one would hope. I imagine salt water for firefighting purposes would only be practical near the coast, but desalination plants in general seem like an overwhelmingly more sensible remedy for water shortages than a multistate pipeline.

Now to see about rallying support for the construction of desalination plants in California...

Kudos, and thanks again for your input!

This is a rather complex solution to a problem that could be solved easily if California simply stopped subsidizing its agricultural water.

Don't touch it!

Seriously, you're right though.

*Columbia River. (Spelling has never been my strong suit.)