I don't like this trend of writing incredibly long articles. It's as if the length alone somehow makes it more intellectual or credible, or perhaps just makes the author look good.
An approx calculation, assuming reading speed of 250wpm, means a 12,000+ word article, like this, will take nearly 1 hour to read.
I'm not deeply interested in the water situation in California, so I probably won't read this, but I don't see a problem with someone bothering to do a detailed story on it.
It was more of a leisurely interesting-but-not-actionable, flavor-of-the-story, Sunday-paper-with-a-bagel read. I wouldn't even call it long-form journalism. It's just bits of history and human interest tied to a current issue with a sprinkling of character and anecdote. Gratifying, not edifying.
That sort of thing has a place, but generally not what I'm looking for on a Wednesday morning.
Did you know that Central Valley almond crop irrigation consumes water equal to 1/2 of a Los Angeles?
But I think you are wrong about the length being a matter of ego stroking. There are legitimate reasons to dive into the details, and given that the Atlantic is relatively internet savvy, there are probably people interested in the content.