Though I had no numbers, I knew that to be true. Acid deposition happens in the absence of rain as well. And as long as the rain or dry deposition happens on ground, the soil immediately goes to work at neutralizing it. Which is why, in streams, most of the acid comes from surface runoff, not from groundwater.
With a frozen ground, you get more runoff and less soil effects, so acid rain is worse in winter in general, even without snow.
With snow, dry deposition collects in the top layer. It gets more acidic the longer the snow lays. And then when it does melt, you have the super acidic snow melt, AND the rain that's melting it, all over a still frozen ground so it's almost all still runoff.
That's why I've said that summer pH readings are not the end-all be all of determining acid trouble. You'd really have to test the worst case winter pH.
I do think that, even without considering rock composition, flat solid land surfaces tend to be bad, rocky scree type surfaces are best. All the nooks and crannies prevent direct runoff and encourage water to enter the soil. Not only that, but at the bottom of a deep pile of rocks, you may be below the frost line and any soil is not frozen.
Anyway, that link is looking at it from the point of view of the forest. Which is likely opposite that of the stream. i.e. stream watchers want the forest soil to take the hit. Forest watchers would rather all the acid flow downstream quickly and not degrade the soil.
Of course, the best of all worlds is to lessen the acid deposition to begin with. Which is happening. I'd imagine the results will be slow for both forest and stream, but slower in the forests.
