Effectively, once you turn a pipe on, you can never turn it off. People who have "senior water rights" are allowed under those state laws to make people "upstream" not only stop using water from rivers, but replace the water that they had been using.
Canada has a large number of rivers that flow north into the Arctic sea. From the US perspective, that water is wasted. "We" would like to see it pumped south. However, we wanted a uniform framework of laws governing that. So we forced the Canadians into accepting water-rights laws substantially similar to the western states' laws. Consequently, the Canadians banned such water exports.
If you want to see how screwed up water distribution is in the US. And how political the mess is, then I recommed that you read the book Cadillac Desert.
And as for the anthropik article, several of the points made in that article (and yes, I know it rambles too much) have to do with how Israel needs the water, and how that water is critical to the security of their nation. When the water being pumped out of the aquifers in Gaza became too contaminated for agriculture, then Gaza ended up getting returned to Palestinian control (and now about all that grows are flowers and hatred). If you look at the "security barrier" on the West Bank, it seems to follow no political nor demographic map. When you map that security barrier against the aquifer's boundaries, then you get a match.
Water is life. And the Babylonians had to struggle with salt deposits in their cropland. As their fields got too salty for high yielding crops like citrus and wheat, they had to switch to lower yielding grains like emmer (good luck finding that outside of a health food store) and barley. Some of those fields ended up so salty that they shine in modern day Iraqi sunlight: those are salt deposits from more than 2000 years ago.
Food is life. Water is life. Without both, we die. Therefore they become political.