Seems like it

Sister Orb immediately called Rean's attention as she told him. [Rean, I can feel it through your hand. It has the same feeling as the natural formation after we entered that cave.]

That confirmed Rean's suspicions, prompting him to reply, "So I was right about the lake water and the river water being two sides of the same coin."

[Although it isn't 100% guaranteed, that's most likely the case. Then again, it isn't hard to guess why. One is basically the byproduct of the other. For you to create the white water in that river, this colored water appears as a side effect. Or, it may be the opposite. For this lake water to appear, that white river is the side effect.]