Being in England with an 18 month on going drought and potentially water stand pipes in the streets this summer, I am not so sure that energy is more important than water. At an extreme, no water or highly polluted water means you die in about a week (depending on climate etc), having no oil, just means returning to a basic life that has existed for most of history. I feel you can get by without oil, but you can't get by without water or at least useable water for agriculture and drinking. I am not sure if there is a shortage of good water or increasing use/wastage of water from a fixed supply in the world.

"Water" is a lot more complex than just the stuff that comes out of your faucet.

Coming to grips with "water" is probably as much an effort as learning about Peak Oil except that water is not burnt and thereby chemically converted into a GreenHouse Gas like CO2 (not to say that H2O is not a GHG itself, which it is.) Thus "water" can theoretically be recycled, which makes it sound like it's no big deal. It is a big deal. Wars are fought over water.

Jared Diamond's book, "Collapse" discusses how water can bring a civilzation to its knees.