Evaporation in a small pond

[Michael from Daytona]

Evaporation is technically one form of "leak." Rates of evaporation depend on several factors. I live in central Florida where my two waterfall-connected 600 gal ponds can develop temperatures in the high 80s (F), which accelerates evaporation to the point where I can lose about an inch of water a day in my 28" deep koi ponds. Relative humidity is another factor. Evaporation is accelerated by low humidity (not a problem here). Surface area is another factor. Smaller, deeper ponds allow less evaporation than wider, shallower ponds. Atomization of water, such as occurs with a waterfall feature, spitter or fountain, creates increased surface area at the interface between water droplets and air and accelerates evaporation. Low barometric pressure increases evaporation rates. Finally, as one reader suggested, wind is a significant contributing factor to evaporation loss.

Ways to retard evaporation include providing pond-side shade plants to keep the sun off the water surface, or utilizing space-occupying semi-submerged plants right in the pond, such as water lilies or water lettuce. Landscaping with dense hedges pond-side can help reduce wind across the pond surface as well.

You can determine how much your waterfall contributes to evaporation by turning off the waterfall for a day and comparing water loss rates. Waterfalls can also lose water in varying amounts at the edges of the feature where splash can go right out of the pond. As you implied, running a waterfall 24/7 can make even a small amount of splash cause a measurable drop in water level over time.

Depending upon the season, I can pretty much predict my evaporation rates. Right now, with the "cool" season upon us, rainfall has been just about offsetting evaporation loss. I don't have access to an irrigation well and for a year had to rely upon city tap water to refill the ponds, and therefore had to pay close attention to chloramine levels so as not to kill my fish (scary to think that the water we're expected to drink will kill fish). So I invested in a rainwater collection system and so far have six connected 55-gallon barrels of additive-free water to top off the ponds.

Good luck with your pond! It looks great.

 

[gwbasley]

We live in Florida and it tends to be very dry in the winter and much warmer than your weather in Georgia. We commonly will add 2 to 3 inches weekly strictly due to evaporation. Our 2 waterfalls probably add to this. During rainy periods, (most of the summer down here), the pond will reach it's overflow run off and we seldom have to add any water.

At one point we developed a leak and the water would drop significantly overnight, (which was how we located the hole and repaired it). I am not suggesting that you ingore it completely, but it seems like normal evaporation.

 

[bggenie]

Here's a thought.... thirsty animals. I have had my pond (3' x 4' x 3 feet deep) go down by 10" overnight when the deer came for drinks!

 

[gwbasley]

However the water loss is occurring, other than a mechanical problem, here is how we solved it so that it takes care of itself.

I rigged up some "works" from a toilet tank using a planting pot, a refrigerator icemaker kit and a few hose and tubing adapters. I then permanently submerged it to a point where it shuts off when the pond reaches it fullest level. I ran the tubing to a hose bib on my irrigation pump and just leave it on. Now, whenever my pond drops by about 2" it automatically comes on and brings it up to full again. An added plus is that I can hear when my pump is pulsing and thereby know when the pond is filling.

 

[poconojoe]

Automatic valves for topping off your water are great if your home's water isn't chlorinated.
I would be careful that such a valve doesn't jamb and cause the water to run constantly. That would be a waste and strain your well pump.

 

[gwbasley]

Automatic valves for topping off your water are great if your home's water isn't chlorinated.
I would be careful that such a valve doesn't jamb and cause the water to run constantly. That would be a waste and strain your well pump.

That is why I hooked it up to my irrigation system...non-chlorinated. I have had this system in use for several years without malfunction and the container is screened over to keep out debris.

Evaporation can be a big issue here in Florida and adding water was becoming time consuming because you had to "baby sit" the hose so as not to overfill the pond. During the hot months this could be every 3 days or so.

 

[poconojoe]

That is why I hooked it up to my irrigation system...non-chlorinated. I have had this system in use for several years without malfunction and the container is screened over to keep out debris.

Evaporation can be a big issue here in Florida and adding water was becoming time consuming because you had to "baby sit" the hose so as not to overfill the pond. During the hot months this could be every 3 days or so.

Awesome!