Arizona on the West Bank of the Colorado River?

  For the most part, the Colorado River forms the western border of Arizona. First it separates Arizona from Nevada and then it separates Arizona from California and, with a few exceptions, the border does not leave the river. One of those exceptions is near the city of Yuma. When the Colorado River flows past Yuma, it briefly flows west for about ten miles before turning south again.  It is in this brief east-west pattern where the border between Arizona and California deviates from the river. There is an old loop of the river on the north side of the present river channel, a short distance northeast of Yuma. I believe the river cut its new channel sometime during World War II, from what I have been told. This old river channel is still very visible on aerial maps and it can be seen from the ground really well to because there is still a line of trees lining the old river channel, with their roots spread wide to suck in the subterranean water. In places, the trees have cut down and part of the old river channel has been plowed up and farmed to take advantage of the high water table that still exists beneath the abandoned river channel. Most of the old river channel is still there, though. In fact, there are  four lakes that exist in the upper part of the old river loop, Haughtelin Lake, Bard Lake and two much smaller lakes that appear to be unnamed. Haughtelin Lake is by far the biggest, it occupies the northwest corner of the loop, the part where the river briefly flowed west and then turned and flowed back south. All of these four lakes are at the upper part of the old river loop.   There is some marshy land between these lakes as well. The line of trees along this old river channel is visible from over a mile away in this desert environment. The subterranean water table beneath the old channel of the Colorado River must be extremely high because it evidently drains a large amount of water into the new channel. The current channel is reduced to almost nothing at Imperial Dam, about 30 miles upstream from Yuma, because two canals, on each side of the river, siphon off 96% of the river's flow, leaving only 4% of the river's flow to continue downstream. After the river passes Imperial Dam and Laguna Dam, just a few miles apart,
 the river is only a few feet wide, with the narrow stream meandering its way in a much wider channel that was formed over the eons. Yet, as the river flows past Yuma, it is wider than it is after it leaves the two dams, but still paltry when compared to the way it used to be. The
Gila River does meet the Colorado River between the dams and Yuma, but the Gila is usually dry.  The Colorado is evidently receiving quite a bit of water from its abandoned channel.
This old river channel is really wide, but then nearly the entire length of the Colorado River was once really wide, before it was siphoned off to nothing to satisfy man's insatiable thirst and need for water.
  I have personally driven across this old river channel. I drove down a well maintained dirt road, on the California side, north of Yuma. I was heading for the line of trees that I mentioned. When I got to the line of trees, I saw an obvious river channel, with deep silt deposits, on the south side of the road, but, on the north side of the road, the old riverbed has been plowed up, so I just saw farmland.
  Usually, when a river, which forms a state or county border, the border stays in the old channel when the river shifts its course. There are a lot of places along the Mississippi, Missouri, Ohio  and Red Rivers, for example, where the state border deviates from the current river channel because the channel shifted over time and the border stayed in the
old channel.
Well, when the Colorado River shifted its course just outside Yuma, it evidently set off a boundary dispute between Arizona and California. Sometime in the 1960s, the two states came to an agreement over how to divide the area within the old river loop. As a result, the state border does not follow the old river channel. Instead, it cuts across the loop with a series of straight lines that make several 90 degree turns.
  Maps of this area do not agree, but most maps show that the land within this old river loop is not part of the adjacent Fort Yuma Indian Reservation, while other maps say it is part of the reservation. Most maps show the Indian reservation encircling this loop of three sides.
  There are other places along the Colorado River in which the state border does not follow the river channel, despite what is shown on maps.