I've never thought much on river foam. But this weekend the river was particularly foamy, especially after rapids. My friend Earl commented, "You have a lot of phosphates in this river; I could wash my clothes in it." My heart sank a little because I had never associated river foam with pollution. I've read water studies on this river and it is pretty good. We speculated that the long drought has left the farmlands surrounding the river unwashed and that this abundance of foam was a sign of 6 months of farm land fertilizers running into the valley. My friend Earl is usually right, but here I hope he is wrong. I found this at another paddler's web site: "River foam is a sure sign of a rising river, you see it on almost any river during the rise, the faster the rise the more foam. It isn't necessarily pollutants: I've seen foam on pristine Rocky Mountain rivers during their rise, and Mark Twain talks about it as a cub pilot in Life of the Mississippi (in the days you could dip your cup into the river water for a refreshing drink). I can only describe foam from personal experience. It seems to emerge from the sandbars as the rising river eats them up. I've always assumed it to be phosphates and sulfates, and other detergent-like substances left in the sandbars from previous river stages. But that is pure conjecture. It appears during the rise, and then disappears when the river crests, or begins to fall again. . .On the Mississippi it often looks like dirty whipped cream. I sometimes joke with my clients: Do you want some root beer float? as we paddle through a slick of it, our passage muffled by the sickly plopping of it as it slides off our paddles and clings to the side of our canoes. Kids are fascinated by it. Adults are usually repulsed."
