That is one for someone to look up. When was it built? Leading up to the 1930's, there was a real belief among the learned, that altering land would alter weather, so if you plowed your fallow fields, it would somehow bring rain. Like a meteorological white man's burden thing.
Anyway, then the dust bowl kind of soured people on that model, since it was only that dusty cause they kept plowing dirt in the first place. But then the soviets picked up on aspects, and just waited for a few million to starve and suddenly there was enough food for the survivors.
I wonder if they built the semi-oval so it would make ocean waves literally push boats up the river toward it.