A hybrid approach would work well too in some situations. When I worked in wetland restoration, one thing we did to reduce the ecological impact of herbicides w

A hybrid approach would work well too in some situations. When I worked in wetland restoration, one thing we did to reduce the ecological impact of herbicides was to cut the weeds a few inches above the water or soil, and then to paint herbicide directly on the cut face with a foam brush. This was a lot more labor intensive than spraying, but reduced the amount of herbicide used by 80-90%, and prevented any from landing in the water via over-spray. Even without the cutting step, applying herbicide directly to the weeds with a brush would be a big improvement over spraying.