You're asking a very hydro-centric question, and I'm happy to try....
I can't quantify that; I'll start with that. However, the idea of developing hydroelectricity and developing reservoirs is a question of how you perceive the development. There is change on the landscape. When you create a reservoir, you're changing a riverine environment to a lacustrine environment, and that is change.
However, to look at it from a different angle, Lac Seul is a huge lake in northern Ontario that was once a river. It has been turned into a world-class wildlife fishery largely because of controlled water and controlled waterpower. In that situation, you've created a very massive reservoir in which, you could argue, the productivity of the fishery has increased as a result of the development, but it was developed first for hydroelectricity.
I have had many conversations with DFO about this, and that's not how they view the Fisheries Act and not how they view compensation offsetting. However, habitat is created when you create large lacustrine environments.
That may take a little bit of a perception change, but to enable that much hydroelectricity to be built.... I'll use another example. The Lower Mattagami River was once a river, and now we have a very slow-moving lacustrine environment that is arguably much more productive than it was in its original state. Wetland has been created, and we now have waterfowl showing up on the backwater wetland pockets. We don't see that as a net benefit of the project; it's just a by-product of the project.