This is from a couple of years ago. It is rubber lined. I have a water well to water the yard and I add water as needed with the well. In the heat of summer it can evaporate a an inch or so in a day.
You can see some fishing line we have strung up. That is supposed to keep the fish eating birds away. A few years ago a Great Blue Heron landed and ate most of our fish. Since we put up the fishing line they have not returned. The migratory birds are Federally protected so to disturb their meal of our expensive fish is against the law. Fortunately our dog did not read the law or we might have lost all the fish.