First, lets have a look at evaporation...what it is, and what it isn’t. Evaporation is caused by water turning into a vapor and escaping from your pond. The amount of water loss will vary according to the region of the country, and the time of year. Ponds that are located in areas of the country with moderate temperatures and high humidity can expect to see 1 to 1 1/2 inches of water loss per week during the spring and summer. Most of this evaporation should be replaced naturally by rain. However, if you live in an area with high temperatures and low humidity, it’s possible to see three inches or more of evaporation in a week.
The quantity and size of your waterfall(s) will also affect the amount of water loss. Regardless of the climate, a 4’x 6’pond with a 20-foot stream and five feet of cascading waterfalls may lose as much as 2 inches or more every day! Why? Splashing and moving water has greater exposure to additional evaporation than the still water in the pond itself. If that same system had a 16’ x 21’ pond, you’d probably never even notice the additional evaporation because it’s a larger pond.
Evaporation is not filling your pond up all the way one evening, and waking up the next morning to find the water six inches lower. That’s a leak! If your pond is experiencing a loss of water at a more rapid rate, you either have a leak, your fish are drinking the water, or your neighbor is taking water from your pond at night to water his lawn. Seriously, let’s figure that it’s a leak. What the heck do you do now?
Stream & Waterfall Leaks
Most leaks occur around the stream or waterfall, so your first line of defense is to carefully inspect the edges of your stream and waterfall. As the dirt around the stream or waterfall settles, it can create low spots that may cause water to escape over the edge of the liner. Keep your eyes peeled for wet mulch or gravel, or muddy areas around the perimeter of your pond. If you find a spot that’s leaking, all you have to do is lift the liner up, and push some soil under it in order to raise the edge. Bingo-leak fixed!
Another possibility is that water is splashing out of your stream. To fix a "splash leak" all you have to do is adjust a few of the rocks under and around your waterfall. This will contain or redirect the splash and it’ll stop the splash leak. Once again, you’ve solved the problem the easy and cost-effective way...using common sense.
Still Leaking? If, after you’ve checked the stream and waterfall, your pond is still losing water, it’s time for a little more work, and some drastic measures. You’ll have to shut your pump off for a day. By doing this, you’ll be able to determine the approximate location of the leak.
Fill the pond water up to the appropriate level.
Unplug the pump.
Let the pond sit for 24 hours.
After 24 hours, check the water level. If the water level of the pond has not dropped, then the leak is NOT in the pond itself.
Check all fittings, plumbing, and pump connections for leaks. The problem may be somewhere in the plumbing. On the Other Hand...
If the water has dropped, you do in fact have a leak in your pond.
To find out where the leak is occurring, allow the water level to continue to drop. The level where the water stops dropping is the level where the leak is located.
Now the fun begins! At this point, you may want to consider calling in a pond professional, but in order to reveal the exact location of the leak you’ll need to:
a. Remove any rocks around the entire perimeter at the level where the water stopped. You can then carefully check for some sort of puncture, or hole in the liner.
b. When you find the culprit, you simply patch it.
c. Patching the hole is fairly easy if you have the right materials. You’ll need a piece of patching material that’s appropriate to the type of liner you have. The best thing at this point is to contact the retailer or contractor to help you with this selection.
d. Finally, apply the patch, replace the rocks, fill the pond back to the top, and enjoy!