Effects of fire on a stream

[wschmitt3 0]

Ash from burnt trees and grass in water makes a caustic or alkaline solution.

[FlaFly 0]

Right. But ash would only be in the original runoff. At some point the soil itself will begin eroding. I was under the impression that very organically rich humus would tend to lower pH. Remember that in a stream, the water doesn't hang around, but continues being replace by water from upstream or tribs. I suspect that ash would be relatively easy to remain in suspension and float on downstream, whereas soil is denser and would be what settles out in the stream bed.

[wschmitt3 0]

You are correct it will wash down stream, I don't know about faster than soil though and humus does lower pH but (bear in mind this is purely theoretical thinking) when I have wet ash in a fire pit or seen wood stove ash piles get wet I have found that it makes a dense sticky paste and I think it would be more persistent than soil and would fill nooks and crannies in the stream bottom and effect pH for at least a little while. I am thinking of worst case scenario here, like a total burn right down to the roots over a large area in a head water mountain stream not a higher order river. In addition to the pH effecting osmoregulation and oxygen/carbon exchange in the fishes gills ash clogs up the gills and chokes them out I would think that this would happen very quickly. Also a very high pH like +11-12 I think will kill fish very very quickly.

 

I don't know though I'm just spit balling here, I would think you would be the expert, I only have taken a a couple semesters worth of classes towards my environmental science degree, you spent 3 decades as an environmental scientist.

[FlaFly 0]

Schmitty... your guesses are as good as mine. Definitely think the initial runoff of ash would physically kill fish. I have trouble believing pH would get as high as 11 or 12, but I would expect very low DO and that would kill fish and invertebrates alike.

[wschmitt3 0]

That's a good point. I didn't think about the DO, there is so many things that can kill fish, it is amazing to me some times that there are any for us to catch.

[flysmallie 0]

In a hundred years it will be like it never happened.

[FlaFly 0]

Too true! in less than 50 years, most of our streams will be under the ocean.

[SilverCreek 0]

Not volcanic ash silver, from forest fires, I believe that wood ash will make the water alkaline.

 

I get it now. Yes, my grandmother used to make soap from grease and wood ash. So that would raise pH.

 

http://www.motherearthnews.com/homesteading-and-livestock/how-to-make-soap-from-ashes-zmaz72jfzfre.aspx