The color differences of the waters you see on the left and on the right side of this bridge are not the result of photo editing (neither is the blue sky). It is a result of a barrier under the bridge separating the water bodies and of putting green color, chlorine and perfume into the left one. This makes the difference: a murky stinky sludge on the right, and a bright green liquid with waves of vanilla smell on the left. The picture is taken at the Northern canal of Caoyang District (Beijing). Even there is dead fish floating belly up everywhere, this does not stop people from fishing in the green part. The color itself I guess is the same you use in soccer stadiums to color the grass and must be harmless. But the water is highly eutrophic and full of algae, and even the artificial coloring keeps it what some people think is pretty, it will be hard to avoid that this flips over with the summer coming. But with scars water resources there is nearly no chance of having fresh water supplies in, there is actually not much which can be done at this stage. Another chance might be to pull out all organic matter mechanically, cut any inlet of nutrients and ventilate the canal with pumps. Not easy to manage at this stage and even it looks silly, perhaps even throwing color in is the best that can be done now. Let's hope for rain. This would bring more options. And by the way, I guess taking a 5 ton truck over this bridge really is no problem - once. Good luck.