Evaporation in Ponds, Streams, Waterfalls and Fountains

Evaporation in Ponds and Lakes from Floating Fountains

A general rule to follow is that most water features will lose about 1 inch per week from evaporation.

Any time you splash water in the air there will be some type of evaporation. How much depends on many factors including:

·         Difference between air and water temperature

·         Wind

·         Sun vs clouds

·         Fall (height of pattern)

·         Droplet size and more…..

All decorative pond aerators or pond fountains that splash at the surface will have the most evaporation. Surface aerators that just bubble and circulate will give the lowest percentage of evaporation per (gallons per minute)

Aeration with the least amount of evaporation

HOWEVER, when there is a water feature with a lower pond and a stream or waterfall above it, there are many variables involved besides just looking at the lower pond and measuring the loss. Here is an example: An upper pond 6´ x 8´, a stream that is 15´ long and about 1´ wide of flowing water, and a lower pond that is about 10´ x 10´. If the calculation is actually one inch of evaporation it would work out to be:

Lower Pond Area: 10´ x 10´ = 100 sq. ft., x 1/12 ft. deep = 8.33 cu. ft. x 7.4805 gal./cu. ft. = 62.3 gallons.

Flowing Stream: 15´ x 1´ = 15 sq. ft., x 1/12 ft. deep = 1.25 cu. ft. x 7.4805 gal./cu. ft. = 9.35 gallons.

Upper Pond Area: 6´ x 8´ = 48 sq. ft., x 1/12 ft. deep = 4 cu. ft. x 7.4805 gal./cu. ft. = 29.2 gallons.

So now there is a total evaporation of 100.85 gallons. But this only affects the level in the lower pond, since the pump is replenishing the upper pond and streambed full of water. Therefore, 100.85 gallons divided by 7.4805 = 13.37 cu. ft. divided by 100 sq. ft. = .13 x 12 in./ft. = 1.6 inches of actual drop in the lower pond for each 1 inch of actual evaporation in the entire pond, stream and waterfall area.

Surface Aerator with very little evaporation

Now we have to add some real variable into the equation, this is the “splash factor” in the streambed and also the waterfall. If it is a very hot summer day and the water is splashing small droplets onto a hot rocks, it will immediately evaporate rather than run back into the stream. Some, naturally, may actually splash completely out of the stream bed. And, do not forget the occasional deer or other animal drinking at night, or neighborhood kids playing, or the large dog taking a swim and taking water out with him.

Also, a hot day with low humidity will obviously have a different evaporation rate compared with a cold and damp day. All of these variables play a role in the evaporation rate. For more helpful pond tips visit Discount Pumps.

Decorative Pond Aerator

Decorative Pond Fountains