The "UFO lookin" structure behind the zoo is the head of a horizontal collector well. That structure goes down as far as the state capitol goes up. No lie. 200 ft deep. At that depth, there are "spokes" called Laterals, that go out horizontally in 360 degrees. They collect the water far below the river. Vertical turbine pumps pull the water upwards. The pump heads are in the UFO. The idea is that the water filters down through the sand, and where it's captured, is relatively clean.
The "new" treatment system actually uses a lesser process to treat the water than before, since the water is "cleaner" to begin with.
There is plenty of water, there is plenty of treatment capacity. There is just issue with getting the treated water to the water tower.
That, and as has been said, usage has spiked. Not JUST because Bismarck has grown rapidly, but also because (regardless of the high river) it hasn't rained.