Shade Balls vs Floating Covers: Which Cuts Dam Evaporation?

Big Ditch builds and repairs farm dams across NSW, Queensland and Victoria and supplies Evap.co shade balls. This guide compares the main evaporation covers using independent figures from the University of Southern Queensland, not supplier claims.

Shade balls vs floating covers at a glance

Option	Evaporation reduction	Capital cost (A$/m², 2020)	Suits storages up to	Modelled cost per ML saved each year
Shade balls and other floating modules	20 to 85%, in proportion to coverage	$20 to $40	About 5 ha	$1,293 to $2,400 (at $40/m²)
Continuous floating cover	70% to above 90%	$15 to $25 installed	About 2 to 5 ha, kept near full	$735 to $1,795 (at $20/m²)
Suspended shade cloth cover	50 to 90%, typically above 70%	$9 to $30	About 5 ha, or 15 ha with internal posts	$394 to $733 (at $13/m²)
Multimolecular chemical film	Under 50%	Product about $14 per litre	About 10 ha	$360 to $1,350
Floating solar panels	In proportion to coverage	Not stated	Depends on power demand	Not stated

Figures are from the 2020 Assessment of Evaporation Mitigation Technologies in Queensland (Schmidt, Pittaway and Scobie, University of Southern Queensland). Cost per megalitre was modelled for eight Queensland towns from Stanthorpe to Mount Isa, assuming the storage stays full all year. Prices are six years old and exclude freight.

How do shade balls compare on cost?

A floating module is any loose floating unit, such as a ball or a hexagonal tile, that covers the water surface without being joined to the next one. Shade balls are the simplest kind.

In the Queensland report, modular covers were the most expensive option per megalitre saved, at $1,293 to $2,400 a year for a $40 per square metre cover. Suspended shade cloth was the cheapest physical cover, at $394 to $733 a year.

At about A$63 per square metre ex GST in late October 2026, Evap.co shade balls sit above the report’s 2020 price range for modular covers. Price them against the value of the water you save, and against the cost of the alternatives on your own site.

When a floating cover is the better choice

A continuous floating cover is a single sheet of plastic, often a bubble-wrap style blanket, that floats on the water and is tied off at the banks. Trials put its saving at 70 percent to above 90 percent.

Floating covers suit small dams kept close to full. The researchers found that ballasting, tethering and removal in dry times limit them to storages of about 2 hectares (Pittaway, Scobie and Schmidt, 2023). Large swings in water level stretch and tear them.

When shade balls are the better choice

Shade balls rise and fall with the water level, fit any shape and need no cables, posts or trenching. You can also buy them in stages and add more later.

They suit tanks, lined ponds and turkey nest dams with a steady level. They work less well on earth dams that dry out, where balls can stick in the mud, and on windy sites, where they can be blown ashore. Read more on how shade balls work.

How to choose an evaporation cover for your dam

1. Measure the surface area your dam holds for most of the year.
2. Estimate the water lost each year from the area and your local evaporation rate.
3. Put a dollar value on each megalitre, such as the cost of carting or buying water.
4. Check how far the level falls in a dry year and whether the dam dries out.
5. Compare the cost per megalitre saved for each option on your site.

Our guide to floating covers and windbreaks covers installation in more detail. If the numbers are close, talk to Big Ditch about your storage.

Frequently Asked Questions

Are shade balls better than a floating cover?

Neither is better everywhere. A continuous floating cover usually saves more water for less money on a small dam kept near full. Shade balls suit tanks, lined ponds and odd-shaped storages where a sheet cover would be hard to fit or anchor.

What is the cheapest way to reduce dam evaporation?

Among physical covers, suspended shade cloth had the lowest modelled cost in the 2020 Queensland report, at $394 to $733 per megalitre saved each year. Chemical films cost less to start but need reapplying about every three weeks and save less water.

Do shade balls work on a farm dam that dries out?

Shade balls are a poor fit for dams that dry out. Balls can stick in the mud as the water falls and may not re-float when the dam refills. They work best on storages that hold a steady level.

Weighing shade balls against a floating cover for your dam? Book a site inspection with Big Ditch and we will help you compare cost per megalitre on your site.