Obviously, the ground water is higher than the pond water. All I can tell you to do is weight it down with big rocks until the ground water goes down.

It isn't exactly the ground water being higher, it is more that the moving ground water is changing the water pressure against the liner. Is there any way you can reduce the amount of water moving in the soil in that area. Maybe you have a rain downspout draining near there? If this is a frequent problem you might want to consider some drainage tile. Sinking a PVC tube vertically on the outside of the pond where the water pressure is greatest can relieve some of the pressure against the liner.

Water seeks it's own level. The pond water level must be at least ground level if the surrounding soil is saturated with rain water. If not as the ground water raises and becomes as high as the pond level the ground water will push up the pond liner as it raises.

So you do not need to put rocks or such to weight the liner back down. You need to fill the pond to the brim. You can improve the drainage in your yard, or you can raise the level of the pond even a few inches above ground level. Then keep your pond level filled to at least ground level. If you do this your pond liner will stay put unless your yard floods inches above ground level.

I hope the way I explained it makes sense...

Lisa

Do you have some sort of overflow for the pond worked out? Or when it rains, does water simply fill to the top of the liner, and then spill over? That was the problem that I had, where water went over the top and got in behind the liner. With my clay soil, this floated the liner.

Since putting in an overflow (simply a piece of PVC that pokes through the liner tightly at the desired max height level), I've had no problems.

David

Thanks david2006 I do have hard clay and after the water from flood started drying the liner went down and I have installed an overflow. My pond is 6 yrs old first time for everything I guess.

David I would say that the overflow will make the problem worse. If overflowing the pond was the problem the liner would not float up as the water level in the pond would always be higher then the water in the ground so the liner would stay down. I would guess what you are seeing is the water in the ground raising the water in the pond until it flows out over the liner. By that time the liner is already floating. With the overflow in the pond now as the water in the ground is higher in the ground is higher then the pond level it raises the liner pushing the water in the pond up to the water level in the ground. As the water gets to overflow more and more water from the pond flows out the overflow and the liner gets higher and higher until there is no more water in the pond. If this doesn't happen then the reason why is that the overflow pipe when installed had to be run to a lower place and it was trenched into the ground and this trench is carrying the water in the ground away from the pond.
Mike