Flowing water

1.Firstly, create a good sized room (300x300x300) and place your info_player_start and a light in there.

2.Create a little channel with a water brush in the middle of it. Give the top surface of the water brush the following attributes:

water
flowing
warp
current_x, where x=the dir of the movement (90 would be pointing to the top of your monitor on your editor's top-down view.)
In the "value" box, lets use 100 for the speed of the water.

3. One more thing must be done for it to flow in the correct direction. Rotate the water texture to the correct current angle. i.e. if your water is headed towards 270 ('south'), then you'd have "current_270" and the texture would be rotated to "270".

4. Add a target_speaker entity right on top of where the water is. Depending on how large your "river" is, you may need more than one. Give the speaker a "sound" of "world/curnt1.wav" (there's more than one running water sound, refer to the sounds listing for the others), an "attenuation" of "-1", and "spawnflags" of "5".

5. Compile your map and check out your flowing water.

Here's a sample map showing the flowing water.