Actually, that isn't water. Its gasoline, sometimes diesel. The barrels are storage for helping drivers who run out of gas on the highway. The empties simply need to be refilled, which is done on weekends at night so as to minimize the impact. Additionally, this is why you frequently see police near these barrels, they can keep their car running all day long but never need to leave. Tow trucks frequently pre-position themselves there for similar reasons.
don't believe me? Crack one open and fill up your tank. Let me know what happens.
