Step One

Find a Suitable Area, or one which you planned to use beforehand.

Now as i almost always start with a flat piece of terrain for my scenarios (like the one above) thats what we will go on, but any area will do really (hell even non flat areas will probably make it easier

Step Two

Use the Roughen Tool to "Rough up" the area you are going to use even if its already roughened, and then use the Smooth tool to flatten it out a bit and make it look like a natural Hilled Area

Step Three

Place Down the Farms so that they curve along with the landscape, making sure that the farm(s) are on both (small)hills and the valleys between

Step Four

After Placing the Farms Down how you want use the Paint Terrain Tool (important it MUST be Paint Terrain Option and not Paint Land or it wont work)
And Chose the terrain "City Tile Pool" and paint the terrain that the farm is on, where the Depressions in the Landscape are (as water Flows downhill and would in real life collect in the lower areas not the Raised ones)

And There you have it, a realistic looking Waterlogged Farms piece of Eyecandy

Tips