Water Evaporates from A Pond

How Much Water Evaporates from A Pond Daily?

It is common to notice that the water level in your pond gradually decreases over time, and the first thing that jumps your mind is: there it goes again, my pond is leaking.

You might be thinking of the cost and the stress of fixing a leak, but This is simply mother nature at work.

The loss you notice is explainable by a natural occurrence, evaporation. Water escapes from the surface of all materials once they are exposed to the heat or wind, and this is what is happening to your pond.

However, you should be a little worried if you lose more than a given amount of water at a given time, probably the water loss might be due to other factors; a leak is the first suspect.

Factors That Affects the Amount of Water Lost to Evaporation?

There are a few conditions that will affect how much water your pond lose to evaporation over time.

Just one of these conditions affecting your pond is enough to affect the amount of water in your pond significantly, and when more than one of these factors are at play, it increases their effect a lot more. These factors include:

  1. Humidity: This is a term given to the amount of water vapor that the atmosphere contains; hence the humidity of an area is high if it has a lot of water vapor in the atmosphere. When the humidity is too high, we notice fogs and what this means is that the atmosphere cannot take in more water vapor from its surroundings. This explains why puddles don’t easily dry out on humid days because the atmosphere is almost saturated with water vapor. It cannot take more. So, if the humidity is high, then the amount of evaporation is reduced and conversely.
  1. Heat: Another way to say this is temperature. If the weather is hot because the sun is high in the sky, what it means is that more water molecules in your pond will absorb more energy from the sun and then escape to the atmosphere. So, on hot, sunny days, as you lose water from your body in the form of sweat, know that your pond is also enduring the same fate.
  2. The surface area of the pond: ponds that are wider in dimension tend to lose more water to evaporation than others. This is because the surface area from which this water can escape from your pond into the atmosphere is larger, meaning that more water will escape.
  3. Shade: the place of shade as a factor in determining evaporation is the effect that shade provided by trees and shrubs can limit the amount of heat that hits your pond. Consequently, only very few water molecules can gain enough energy to escape to the atmosphere.
  4. Plants: plants that grow in water like water lilies affect the amount of water you lose from your pond. These plants have a way of covering the surface of your pond so that only a few spots are exposed. Remember, the water lost through evaporation is from your pond surface, so when these plants cover your pond surface, the evaporation rate will greatly reduce.
  5. Wind: wind has a way of carrying a lot of things; if a strong wind can carry the roof of a house, what makes you think your pond water will be spared.

When the velocity of the wind is high, it will carry away many water molecules from your water surface. Hence the stronger and frequent the wind, the more water you should expect to lose by evaporation.

On What Type of Days Will the Most Pond Water Evaporates?

Normally some factors will affect the amount of water evaporating from a pond. A closer look at them will tell you when to expect high or low evaporation.

Since the increase in heat, wind speed, and a decrease in relative humidity will cause more water to be lost from your pond through evaporation, therefore, hot, windy, and dry days will see your pond losing more water.

How To Tell If Your Pond Is Leaking or Evaporating

We will attempt a simple experiment to show how to determine if the water loss in your pond is due to a leak or evaporation.

  1. Fill your pool to its normal height. Market the height of the pond and record.
  2. Get a bucket, fill it with water but not to the brim, mark the water level in the bucket and record it.
  3. Place the bucket of water very close to the pond in such a place that the same wind speed or heat that reaches the pond will get to the bucket. Make sure that nothing is shading the bucket because you want the pond and the bucket ‘ to have the same experience “. The bucket is your control in this experiment.
  4. Leave the set up like that undisturbed for 24 and then mark and record the decrease in the pond’s water level and the bucket.
  5. Repeat the same procedure, leave the set-up for another 24 hours, and note and document the result.
  6. Now, take the average amount of water lost in the pond in those two procedures and the average water loss from the bucket.
  7. The verdict: if the water loss in the bucket per unit area is the same as that of the bucket, then the water loss in your pond is due to evaporation; however, if there is a significant difference between the water loss in the pond and that in the bucket, it then means you probably leak your pond.

Pond Water Evaporation Rate Calculator

On average, a pond will lose an inch or a maximum of 3 weekly to evaporation. Daily, it will lose about 0.5% of the water pumped into it on cold, humid days, while it will be about 1% on hot, windy days.

Hope you are up for a little math (we can’t help but do a little calculation)

Let us illustrate how to calculate the exact amount of water your pond loses daily from your pond.

Let’s assume your pond gets 1200 gallons of water per hour from your pump.

Then the amount of water you will lose will be:

0.5/100 ×1200 =6 gallons of water

This is assuming that the day is cold and humid and only 0.5% is list

On hot, windy days, the water loss will be:

0.6/100 ×1200 =12 gallons.

Hence 12 gallons will be lost in the given pond on hot, windy days.

The next question you might want to ask is how I know the number of gallons of water my pump gives out an hour.

The answer is in another little math.

You must calculate the head pressure of your pump and the way to do it is this:

I foot of vertical lift = 1 head pressure

10 feet of horizontal distance = 1 head pressure.

(Vertical lift which is the height from where your pump sits to the height to where the water is to be pumped, while the horizontal distance is the ground distance from where the pump sit to where the pond is)

So, assuming the vertical lift of your pump is 3 feet, and the distance between your pump and is 20 feet, then your head pressure will be:

3 + 20/10 = 5

With the head pressure at 5, all you need to do is to check the chart of your pump, and then you can know how many gallons of water your pump can give out at a head pressure of 5.

How To Stop Your Pond from Evaporating

The following ways can be used to reduce the evaporation rate because, in the real sense, you cannot stop evaporation. After all, it is a natural phenomenon.

  1. Reduce the surface area using aquatic plants such as duckweed and water lilies that cover most of the surface of your pond.
  2. Plant tall bushes and shrubs around the outside of the pond to provide shade from the heat of the sun.
  3. Non-toxic dye and film can be poured on the pond surface to reduce the penetration of the ultraviolet rays of the sun from hitting your pond surface and helping to evaporate water from your pond.

How To Maintain Water Level in A Pond

Different devices can be used to maintain your pond’s water level, including the mounted pond water regulator, below ground auto-fill canister, electronic water control alarm system, and the likes.

The pond auto fill valve is a very simple device used to maintain your pond’s water level. The valve of the device rests on the surface of the pond, and as the water level drops, the valve will sink, which will prompt the door of the valve to open, causing water to be released to the hose connected to the inlet into the pond. As the water level rises subsequently, the valve door closes, and then the water flow stops.


Evaporation is responsible in most cases for the water loss in our ponds if it is within an acceptable range of about 1 to 3 inches weekly.

If, however, the rate of loss is greater than normal, then you might be dealing with a leak, and a little troubleshooting can tell you where the leak is from.

You can easily determine If you are dealing with a leak or evaporation in your pond, and there are numerous ways to reduce the evaporation rate, too, if you must. Just go ahead and install a device to maintain the water level in your pond; that will save you a lot of hassle.

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