Sometimes you just have to pay attention...look what's around. Why would THIS be sitting HERE. If man made it, there's a reason (at least in most zip codes). The T & P Railroad, as it chuggged east to west through our stretch of Texas, had to stop for water at pre-determined intervals (1 - 3 miles sometimes). We're used to seeing the wooden elevated water tanks near train depots from childhood Western movies, but sometimes, if a stream ran nearby, the crew that built the railroad also dammed up the stream for the locomotives to drink.