Pond bottom now floating

[ponderoni]

I have a smallish backyard pond with a problem.
It is about two-and-a-half feet deep with quite a few water lilies in it and some feeder goldfish that have been living in it for years.
Last fall, I noticed that the entire bottom of the pond had risen up about a foot.
Now it has risen to within a few inches of the surface. Lily rhizomes are clearly visible.

Although a lot of the fish survived last winter, I am concerned about the coming one which is supposed to be harsher.
Aside from that, it looks rather unsightly.

How do I get the pond bottom back where it belongs?

 

[poconojoe]

I think you may have what some call a water hippo.
It's when water accumulates under the liner which of course forces the liner up.

One of the remedies is to add a way for the trapped water to find a easy way to escape.

This is done by slipping a vertical piece of pipe between the liner and the pond wall. The pipe is positioned with one end all the way down to the trapped water and the open end above the pond. The pressure of all the water in your pond should force the trapped water up and out.
You can use a piece of PVC pipe or something similar that's ridgid and won't collapse.

It should be pretty easy to do.

Hope this helps.

 

[j.w]

@ponderoni

 

[Lisak1]

Yup. That's a hippo.

 

[ponderoni]

Looks like I misled everyone.

The phenomenon has been less distinct in the last few days.
This afternoon, I got on the waders and walked around in the pond, feeling the bottom with my bare hand.
Solid as the hardpan I dug into originally. No squishy bits at all. Hard bottom.
This evening I noticed that everything looked "normal" again.
Deep water, no visible rhizomes.

I wonder if I just unleashed trapped gas bubbles or whatnot.
I definitely stirred up years of sediment, which seems to have settled quickly.

I'm quite open to suggestions and will keep my eyes open for the hippo.
I had some watermelon beside the pond this afternoon, so that might have placated the hippo spirit.

Thank you all for your input.

 

[Lisak1]

So the liner WASNT floating? Or you walked on it and it settled back down?

 

[Jhn]

The hippo effect will only happen when it rains, its not a matter of how hard the bottom of your pond is, it matters more what type of soils you have and where run off during rain storms ends up.

 

[IanS]

If your pond water level is below the garden/ground water level then the ground water will push up the bottom of the liner. Basic hydraulics. The water levels try to even themselves out.

At all times you want to try to keep your pond water level higher than the ground water level - the weight of that water above the ground will weigh the hippo liner down - ie stop it rising.

 

[GBBUDD]

Water takes the path of least resistance . And in your case you have a hard packed soils soils . To the point draining is not happening . So the next choice is to push up f t on under the liner simy lifting a sheet of rubber.
Solution is to make an easier path for the water to go. Or you can add several tons of stone and cover the liner make that a hard to go path as it talks a lot of pressure to lift the rocks

 

[beetroot]

I have a smallish backyard pond with a problem.
It is about two-and-a-half feet deep with quite a few water lilies in it and some feeder goldfish that have been living in it for years.
Last fall, I noticed that the entire bottom of the pond had risen up about a foot.
Now it has risen to within a few inches of the surface. Lily rhizomes are clearly visible.

Although a lot of the fish survived last winter, I am concerned about the coming one which is supposed to be harsher.
Aside from that, it looks rather unsightly.

How do I get the pond bottom back where it belongs?

FOR PONDERONI, I had exactly the same problem last year, with lifting liner. My 4x4ft small ponds liner bubbled up at the bottom and sides with water. It would subside and bubble again with heavy rain. This year in July, I enlarged it to 6x4ft. I didn't need to but thought I may as well if I'm doing work on the pond. I did a berm around with well compacted soil and also did a gravel trench dropping the liner down into it. The bigger pond looks better, as I've also added shelves each end for baskets for plants and goldfish now too A big job for a 67yr old woman but well worth all the hard work, so far so good . Just to add a big thank you to everyone on here that gave me the advise of how to solve my bulging liner problem

 

[beetroot]

FOR PONDERONI, I had exactly the same problem last year, with lifting liner. My 4x4ft small ponds liner bubbled up at the bottom and sides with water. It would subside and bubble again with heavy rain. This year in July, I enlarged it to 6x4ft. I didn't need to but thought I may as well if I'm doing work on the pond. I did a berm around with well compacted soil and also did a gravel trench dropping the liner down into it. The bigger pond looks better, as I've also added shelves each end for baskets for plants and goldfish now too A big job for a 67yr old woman but well worth all the hard work, so far so good . Just to add a big thank you to everyone on here that gave me the advise of how to solve my bulging liner problem

 

[Lisak1]

Wow @beetroot - kudos to you! I don't think I've ever seen astroturf applied that way around the pond, but you've done a great job!

 

[beetroot]

Wow @beetroot - kudos to you! I don't think I've ever seen astroturf applied that way around the pond, but you've done a great job!

Thank you so much. Even the Astro turf in the garden is my work I've very proud of myself