The idea of this little tweak is to make the river appear more like it would in the summer. Nice idea of Nicossalonso. It does involve editing one of the xml files of the game so no clue what this will do to mp or achievements.
Download the zip and replace the file steam\steamapps\common\Spintires\Media\classes\waters\blue.xml
And then you get this, screenshot courtesy of Nicossalonso.