One Second Rush
Here is an 8-stitch panoramic shot of Niagara River in Upstate New York. The distance, speed and massiveness of the water would only require 1 second for me. But it really depends on your taste.
I set the shutter at 1 second, ISO 100, white balance daylight and from there adjusted the aperture or F-stop to meter to F/10. This was shot when the sun was almost out hence the F/10 aperture.
The walks in Niagara Falls Park are under construction. Only a small portion near the waterfall where tourist are allowed. If you want a better spot go to the Canadian side. 🙂