Disappearing water.

[David G]

Having dug and lined my pond, (approx. 3x4m kidney shaped) filled it and introduced a few plants we had a lot of rain one evening/overnight. In the morning the water level had dropped by over a foot. Checked for leaks, no sign, then syphoned out all the water cleaned the liner still nothing. We have quite a high water table and have read that it can cause bubbling. Would that be enough to push tens of gallons out over the edge? Is there anything I can do other than start again higher up the garden?
Thanks

 

[Mayank]

Every time we lost water and thought it was the liner or the tub was cracked or whatever, it was always from the waterfall area so water was either bouncing off the rocks and exiting the pond or leaking from the side. You'd think it was minimal because it just seemed like tiny droplets but I guess it adds up!

 

[j.w]

@David G
Maybe a photo of your pond and area around it would help us help you figure this out?

 

[Mmathis]

Hello and welcome!

Do you have a waterfall, or any areas where the level of the edges is lower than the rest of the pond?

We have a high water table, as well. When we re-did our pond 2 years after we built it, we had enough liner (never cut off excess liner!) that we were able to build the pond edge up enough that the pond water level was 6-12” above ground level. That pressure will help combat the “water hippos.”

I honestly don’t know how much water would be forced out of the pond by the “water hippos,” but I imagine that it could happen.

Please post some pictures of your pond so we can see what you are talking about. We love to see pond pictures!

 

[David G]

Ok thanks, here are two photos one represents mid-afternoon before the heavy rain and the other the following morning. I must also say that during wet winter periods the ground at that end of the garden can get quite waterlogged.

 

[j.w]

I don't see anything that looks disrupted due to a bubble up but then I have never had this happen so maybe after it bubbles up it goes back down to the same shape it was. Have you added water back now to see if it still holds water now? Very strange if it does. Looks like you don't have a waterfall right or is that one where the moss is on the left?

 

[IPA]

Welcome, Nice looking pond. Hope you get it figured out. @GBBUDD might have a few ideas.

 

[addy1]

Welcome to our forum!

Wowo that is a lot of water to poof away!

 

[GBBUDD]

well it looks like there are no fish so thats a plus . shut down all water flow with the pond at a level you know is above tge leak and let the water level drop. At the same time every day or two or three times a day AT THE SAME SPOT IN THE POND measure how much water you have lost and do this until you get no water loss . at that point your leak is going to be at the water line somewhere in the pond or slightly higher then the water line. if you have more tgen one some simple math on your reading should tell you. Good luck
I will add this is your liner under the row of bricks us that as high as your liner goes if so don't you also get water runoff when it rains into your pond

 

[Lisak1]

OK, but the weird part is the huge water loss AFTER a big rain. And I don't even see a waterfall - am I missing it?

I think it's entirely possible you got a "hippo" under water that pushed the liner up and evacuated the water. Then the water level under the liner went down and everything settled back in place. What kind of liner is that? It doesn't look to be 45 mil EPDM, but pictures can be deceiving.

 

[David G]

No waterfall, it was planned as a simple wildlife pond. As you might imagine I have given this a lot of thought over the past few days.The last response (a 'hippo') seems the most likely to me. It rained more a couple of days later and the water level went up by about an inch and seemed to stay. At that point I thought that maybe a leak had somehow sealed itself, but I couldn't find any evidence. There is a wide seam but I checked every inch and it is secure. The next step was do drain the pond which again with a 'fingertip search' revealed no leak. I have considered laying another different type of liner on top but needed to know why it happened in the first place. A new liner would in any case mean removing the bricks and stones which I have now done and pulled the lner out onto the grass brushed it off and cleaned it and still no sign of a leak. If it did hippo it is an impressive amount of water to lose in one go but as I say I think after very heavy rain the water table probably rises all the way to the surface, if that is the case simply raising the sides of the pond (another idea) might not be enough to solve the problem especially in the winter months.
Yes it is and LDPE liner with a 40 year guarantee!!

 

[IPA]

I was thinking about the hippo too. If it was and the water table rises as much as you say than maybe there is no option other than moving the pond. I guess I’d fill the pond when it isn’t supposed to rain for a few days and see if the water level is stable.

 

[poconojoe]

That's a lot of water loss. I would leave it and see if it keeps draining down. If it stays at that level, fill it up and then watch for it to drain down. If it drains down and stops, your leak is at that level. If it doesn't drain down, then maybe the hippo idea is valid, but again, that's a lot of water. If that's the case, there must be a really high water table or an underground stream.

I also have concern for the height of your perimeter or edge. With those bricks flush like that, your liner is actually below grade. Ground run-off will certainly flow into the pond and that's not good. Pick up the bricks, build soil under the liner to bring it above grade, then add your bricks back.

 

[JamieB]

You could try adding more rock to the bottom and sides, to use the weight of something denser than water to prevent a " hippo" from being able to bulge in. I'd suggest large flat rock's, but make sure They are not so heavy you need help to move them, not should you go for rough edges kind to prevent damage to the liner.

 

[David G]

You could try adding more rock to the bottom and sides, to use the weight of something denser than water to prevent a " hippo" from being able to bulge in. I'd suggest large flat rock's, but make sure They are not so heavy you need help to move them, not should you go for rough edges kind to prevent damage to the liner.

Thanks, I have considered that but am concerned that this might just displace any pressure to the sides. Incidentally a previous contributor mentioned avoiding ground water running in. I'm not sure what the problem is there as all water would be running off our garden which is free of pollutants, pesticides etc.