I always do it like this and this is my personal preference. I have this program called Display Driver Uninstalled (driver sweeper), that you can get from Guru3D.com . Then I restart my pc and boot up in Safe mode and in safe mode I uninstall video drivers and i also use CCleaner to make sure registry has no errors. After I have done that I boot up again and now I'm ready to do a clean install with no trace of my previous drivers.
Sometimes if you just go and uninstall video drivers like any other program, you might be left with some nasty registry errors or so and it will start messing with your new drivers.
Now i know this method takes a little bit longer, but you want your games to work right? I will not guarantee that this will fix your problem tho.
Using more than 2 water sources, will make your maps optimization a lot worse for low-mid or even high end PC's. The games might become really laggy, its because every water source you make on the map, will render twice which takes up even more RAM from a game that already eats your 8GB like it was nothing. My suggestion is to connect 1-2 water source out of the boundaries, where the player wont see it (OOB area), if you do this before you proceed, will cut you a lot of headache later.
OnkleSam's map "crossing in the woods"- river is connected outside of the playing area so its actually only 1 water source used. And Relic uses it as well on their maps.