Can someone give me some tips on shooting waterfalls at long exposures in daylight?

Here's a couple of tutorials (of sorts) that address your inquiry:

"How to Shoot Waterfalls" ... by Greg Disch Photography.

Of note, for the above ... is the mention of the use of filters. Notably; Polarizer and Neutral Density.

Camera settings are covered as well.


"Tips For Long Exposure Waterfall Photography" ... by Alex Wise.

I tried this once, with disappointing results. From memory I think I had sharply contrasting areas of sunlight and shade which were exaggerated by the prolonged exposure and that made the result unappealing.

If your shooting in the sun you will almost certainly need a neutral density filter to cut down the amount of light. Other than that...

I see you have done HDR so I will suggest using that to your advantage. Set it up so that the middle exposure will be no more than 1/8 second and go 2 stops over and under from there. Start with a longer exposure if you want the water to become completely milky smooth.
This is one I did using this method and manually blending the shots in Photoshop.(Manually masked in layers. Not merge to HDR.)
Duvall Branch
It is much much easier on an overcast day. just setup the shot for a 1/8 second or longer exposure. Should look something like this - The falls

Thanks for the tips my Friends!