A client of mine had a company come and dig a large pond.
Over the space of about 3 months, it was virtually dry in the summer. Could this really be down to evaporation, or is it more likely to have a leak?
To fill it, I had a 3" pump going most of the day, so many 1,000's of litres have disappeared.
I have read on the internet, that for a pool, 1/4" a day could be lost due to evaporation, but for outside, it depends on average wind speed, temperature, etc for an accurate calculation, which is pretty much impossible. It also describes a "bucket test" - put a bucket in so that it is under water, then monitor whether the level of the bucket drops at the same rate that the pool does, as evaporation should be the same for both - does that sound reasonable for a pond?
As my visits to this client have just resumed, I went there about 4 weeks ago, and it was a foot or so down, but this week, it was pretty much as the second photo - we have not had any rain to speak of for weeks down here, and it is topped up from the rainwater run-off from the roof of the property.
The company that installed it are being very cagey about coming back to site, and are just quoting that they have seen the same at a number of other sites, so is all down to the lack of rainfall in the summer. The lining is some sort of clay impregnated rubber, which sounded very impressive when they were talking about its self-healing characteristics, and it has a deep layer of soil on top of the liner.
I would be interested to know what others would use as a rule of thumb for acceptable water loss.