Here is an image that shows soil erosion colored brown waterflow on the left while the main spillway is white (not brown). Contrast this with the image(s) in post 1,326. The "browning" is from sediment material via erosion entering into a waterflow. The waterflow on the outside edge of the sidewall is white at the time of this photo.
In this pre-failure stage of the Main Spillway, brown water signaled the undermining of the concrete slabs in the main spillway. Notice the tremendous side flow of brown water on the outside edge of the containment wall.
The importance of this image is that "brown water" in the main flow could indicate a source in the main spillway that injected a burst of substrate material. However, the more likely case is an injection of material at/near the main spillway blowout.
im just sayin... did that really have to be explained??