aelf
Ashen One
Poison water supply is indeed annoying, but it seems to only happen during wartime. Or maybe only AIs who aren't pleased with you will do it, so manage your diplomacy well. As for fomenting unhappiness, same story, and I think you should have enough EPs to prevent that from happening more than a few times if you play well (amount of EPs the target has compared to yours affects the cost of missions, I think).