I like concrete around a waterer with about a 4" step up 12" larger than the waterer as it keeps manure out of the waterer - cows don't back up to it and take a dump. The large concrete pad also avoids a mud hole around the waterer and is easier to scrape manure off than rock etc. 

The concrete also bridges the 6 ft deep waterline trench and with enough rebar will stay in one piece even as the trench area settles over the years. The main pad will slope slightly downhill toward the corn in the distance to drain with the waterer drain on that side. The waterer and small raised area around it will be level.

The whole pad should be a bit higher/step up from the surrounding soil to keep heavy rains from washing mud etc across it.  If the edge starts getting too high I will dump some screenings around the edges the cattle use for access.

Thank you. I am pleased with how the shed and feeding area are turning out. Now need to get the fencing around it up.

Jim