You can, with care, obtain the same effect - even better actually - as a 1 stop grad ND filter. What you need to do is take identical shots of the same scene at different exposures. This photo would really work well with the technique. If your camera permits automatic bracketing, that should help even more.
For example, if your camera allows -1, +1 and 0 braketing, then say expose for the trees and the -1 shot will be one under, darkening the skies. If your camera doesn't have auto braketing, then you just have to be careful to not disturb anything before taking the second shot. I assume you used a tripod for this photo. Obviously it is necessary to use one with this method. And of course the method can be used for 2, 3, 4 stops as well.
You need PhotoShop to do the post work, but it is not hard at all.
If you are interested in the details of what to do in PS, send me an e-mail and I will attach the list of steps in a reply.
If the original is a slide or negative, then the same techniques can be used when scanning (assuming the info is there in the slide or neg).
Gale, thanks for your comments. Our area has many small beatiful lakes and many of them are world class fly-fishing lakes. However, you people down in Florida have all those colorful birds - so I guess it evens out.
John, thanks for your offer. I did shoot with a tripod but wasn't using my remote shutter release. I took several shots from a few different locations along the lake shore. In some locations I did bracket the shots but on my camera its not automatic - you have to press the shutter for each shot so I just manually changed the shutter speed. This particular shot, which I liked the best, was one of the ones I didn't bracket Another problem was the clouds were moving very fast - visible motion in 9s between two of my shots. I'm currently taking a Photshop course and I think I have some idea of what to do but if I get stuck trying this sometime, I may take you up on your kind offer.