Man made ponds need oxygen if they are stocked with fish. Some ponds that are shallow need them more than deeper ponds. The pond that is in the picture is about 20 feet deep in the middle, so it creates a lot of oxygen in the water.
You can buy a pond areator to put in your pond, deep or not, just to add extra oxygen into the water. You can adjust the controls on the aerator so that you can have a nice looking spray come up from the pond, or just have it running a little just for the purpose of having the oxygen in the water.
There are many sizes and types of aerators out there, so you might want to shop around. All you need is the aerator, some pvc pipe, water supply with good pressure and you're ready to go. If you're adding the aerator to an existing pond, it's a little tougher. You may want to let the water go down a bit so that you can work with the pvc pipe. You don't want your pvc pipe showing, that is tacky.