Let me suggest you following:
Considering, you are running the game in OpenGL, you can choose a different kind of Antialiasing: FXAA
You need the Nvidia Inspector, a powerfull tool, which can enhance the poor default driver settings by unhiding hidden features. You can also overclock there, but thats not my suggestion.
http://downloads.guru3d.com/NVIDIA-I...load-2612.html
Once started, you need to push the 'Profile Driver Settings' button.
I suggest to choose the IL-2 FB/PF profile (or else it will be used on any 3D application). You can disable any of the normal Antialiasing modes and then scroll down and find the FXAA entry very below. Set it to '0x00000001'.
Start the game and see, if you like it.
This AA mode can also smooth the river edges.