Q.
From GCMRiff: Do you have any info or opinions
on the effects of small scale gold suction dredging?
A.
Yes, in both cases. First of all, I'm not sure
just what you mean by "small scale gold suction
dredging." This could range from one guy in a
SCUBA outfit suctioning stream beds to a "small
scale" commercial operation. If you could be
more specific, I might give you a better response
than what is below.
Any suction dredging of streams can and probably
will have a deleterious effect on the ecology of
a stream; the scale of the operation is what is
important. At a minimum, it will probably destroy
the benthic invertebrates living on and among the
stones that are dislodged. Some of these may survive
and drift downstream, but some will not. This is a
direct physical impact. On top of that, the silt and
fine sand stirred up will settle out on the stones
ownstream, coating the algae and invertebrates with
a layer of sediments that can wipe them out. This
material can also be harmful to salmonid reproduction
if the suspended sediments settle in redds and suffocate
the developing embryos. Now a single diver turning over
stones in pools looking for nuggets probably won't have
a serious impact, but escalation from this will result
in an escalation of the impacts. There is a lot of
scientific information published on the impacts of
dredging on stream ecology, and this would be applicable
whether they were dredging for gold or gravel. All of it
says essentially what I've said above; the impacts are
mainly from physical disruption of the habitat and the
downstream impact of the suspended sediments. In some
cases, chemical impacts can also result if the dredging
operation introduces chemicals into the stream or alters
the natural chemical regime.
If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584
Email: streamdoctor@aol.com
The 'Stream Doctor' is a retired professional stream ecologist and
author, now living in the West and spending way too much time
fly-fishing. You are invited to submit questions relating to
anything stream related directly to him for use in this Q & A Feature
at streamdoctor@aol.com.
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