Flowing water long exposures

[CaraRose]

These four are Alberta falls and the Alberta Falls trail in Rocky Mountain National Park.

I'm curious, how do most people deal with the contrast when you have dark rock and white water from the waterfalls? I feel like a lot of my long exposure waterfalls ended up with the water fall itself being somewhat over exposed.

I'm especially curious about the two middle ones-- does the effect work? Or should I have gone for a faster shutter speed? The water was extremely fast moving, but I worry if it becomes a bit too strange when the water turns to pure white like that.

The last one I like the water flow, but I think the picture itself is just too dull color wise.

Opinions are welcome! I'm trying my darndest to get better with flowing water shots.