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RE: dam-l micro hydro vs large hydro
Response/comments on Dianne's questions
Perhaps some definitions might be helpful. I've just flipped open a
small hydro workbook that was put out by Energy Mines and Resources
Canada in 1987.
Micro hydro is defined as up to 25 kW, mini hydro as up to 1 MW and
small hydro as up to 20 MW..
I'd be curious to regarding what others had to say about impacts of
smaller hydro operations.
I'd agree that impacts of mini/micro hydro would be more diffuse, and
should be addressed in a cumulative way. I haven't read a lot about
impacts of small/mini/hydro however I have heard of impacts related to
plant start up/shut down. Often small hydro plants are off channel and
remove water upstream then return it downstream. I think the impacts
would also arise when a large proportion of the flow is diverted out ot
the channel and into penstocks. Another possible impact is related to
the use of smaller facilities for peaking. One proposed hydro plant I
am assessing has a small headpond (i.e. reservoir) so that in the low
flow season they can store enough water to allow generation while still
passing sufficient flows down the natural channel to sustain fish. If a
hydro plant such as this were to reintroduce the peak flows into the
creek downstream then it would no doubt have impacts. Peaking impacts
are fairly widely recognized (but they still occur).
I am very curious though whether others have comments on hydro-electric
generation which takes advantage of head at natural cascades. From a
fish(eries) point of view cascades very often represent barriers to fish
passage. Therefore dams should not cause fish passage problems, and
without a reservoir they should not alter the hydrograph. As far as I
can see that would be quite benign. Do others have comments here?
My comment on run of the river is that I think the term is often
misapplied. It may be a simple point, but they are still dams which can
certainly block passage and some may have a large reservoir to create
head. I regularly see it applied to reservoirs/dams that do not alter
the annual hydrograph (i.e. no storage from one season to another), but
DO alter flows on a daily scale (i.e. peaking). In my view this is
misapplication of the term run of the river. I think it should only be
applied if there is no alteration to the hydrograph at any time scale
(they might still have reservoirs within this definition Also run of the
river dams can definitely blockupstream fish passage and certainly
cause problems for downstream fish passage.
Steve McAdam