Welcome to this forum!
I also keep my hives in an ant environment. The water-trap works nicely, but be sure not to get any long grass or anything near the hive gowing high and touching the hive and thus making a bridge for the ants. If your area is very hot and you can risk loosing all the water to damp, you can add a bit of (food type of) oil on the top of the water, and you won't loose as much.
My water trap worked like a charm, but I had to make some sort of roof over it as I lost quite a lot of bees without it. They missed the landing board and hit the oily water and died.
As I have the same ant problems as you, I would be glad to hear about any other tips or trick you might have