Australia’s farm dams are losing water at a rate most property owners underestimate. If you manage a dam — whether on a farm, a mine site, or an infrastructure project — chances are that evaporation is silently draining your storage every single day.
Understanding what evaporation is and how it affects your dam is the first step. The next step is doing something about it.
This guide covers five proven methods to reduce evaporation loss from farm dams in Australia, with data on effectiveness and cost so you can make the right decision for your situation.
Why Reducing Dam Evaporation Matters in Australia
Australia is one of the driest inhabited continents on Earth, and our water storages are under constant pressure from evaporation. According to the NCEA Australia evaporation calculator, some regions lose up to two metres of water storage depth annually — that’s roughly 20% of a dam’s total content disappearing into the atmosphere each year.
For Queensland farm dam operators, the numbers are even more confronting. Research from the University of Southern Queensland (UniSQ) shows that evaporative loss accounts for 30 to 40% of the total volume held in most Queensland farm storages annually, with evaporation rates in the Granite Belt Region alone reaching 1.6 to 1.8 metres per year.
Agriculture Victoria notes that in shallow dams located in low-rainfall zones, total annual evaporative loss can reach up to 50% of the dam’s total storage volume.
Three core concerns drive Australian dam operators to act:
- Capturing rainfall effectively — Maximising every rainfall event when inflows are already limited
- Preventing ongoing water loss — Reducing the daily drain on stored volume through evaporation
- Managing algae growth — Reducing light and temperature at the water surface to inhibit algal blooms
5 Methods to Reduce Evaporation Loss in Farm Dams
1. Optimise Your Dam Design to Minimise Surface Exposure
The most permanent solution to evaporation is also the most structural: design your dam to minimise the water surface area relative to its volume.
Evaporation occurs at the water’s surface, so the surface-to-volume ratio is the key variable. A narrow, deep dam loses far less water proportionally than a wide, shallow one.
Key design strategies include:
- Increase depth rather than width — Dams deeper than three metres retain cooler water, which evaporates at a lower rate. Agriculture Victoria confirms that deep dams lose a lower proportion of their total stored water to evaporation than shallow ones.
- Subdivide large storages into cells — Splitting one large, wide storage into multiple smaller, deeper cells reduces the total surface area exposed at any one time.
- Consolidate multiple small dams — Fewer, larger dams are more efficient than many smaller ones; the surface area to volume ratio improves at scale.
Evaporation reduction potential: 20–30%
For an introduction to the science of evaporation and why surface area is so critical, see our introduction to evaporation.
2. Use Windbreaks and Shade Strategies
Wind accelerates evaporation by constantly replacing the humid air layer sitting above the water surface with drier air from the surrounding environment. Reducing wind speed at the water surface directly reduces the rate of evaporation.
Shelterbelts — rows of trees planted perpendicular to the prevailing wind — can reduce evaporation by up to 30% for smaller, regularly shaped storages under one hectare, according to UniSQ research.
Important limitations to keep in mind:
- Most effective for storages smaller than one hectare with regular shapes
- Trees take years to establish before delivering a meaningful windbreak effect
- Roots can affect dam walls if planted too close
- Large, irregularly shaped storages gain limited benefit
Evaporation reduction potential: 20–30% (small, regular storages only)
3. Install Evaporation Control Covers
Physical covers are the most effective evaporation reduction technology available. By creating a barrier between the water surface and the atmosphere, they block the evaporative process directly — regardless of temperature, wind, or sunlight.
Floating Covers
Continuous floating covers are placed directly on the water surface, physically preventing the exchange of moisture between the water and the air above.
- Constructed from polyethylene, polystyrene, foam, or reinforced wax-coated materials
- With full surface coverage, floating covers can reduce evaporation by up to 100%
- Also prevent algae growth by blocking sunlight from reaching the water
- Examples include Aquacaps and E-Vapcap products
Suspended Shade Structures
Rather than floating on the water, suspended shade structures are cable-tensioned above it. This design:
- Traps a layer of humid air between the cover and the water surface, slowing evaporation
- Remains unaffected by changing water levels
- Allows rainfall to pass through the permeable fabric
- Reduces wind and solar radiation at the water surface
UniSQ research has found that suspended covers can reduce evaporative loss by up to 90% while also improving water quality by inhibiting algal growth.
Modular / Shade Ball Covers
Modular covers consist of individual floating units — including shade balls and interlocking cap designs — that are deployed across the water surface. They are:
- Incrementally deployable, allowing costs to be spread over time
- Self-adjusting with water level changes
- Able to reduce evaporation by up to 85% once full surface coverage is achieved
- Proportionally effective at partial coverage
Shade balls are particularly well suited to industrial water storages, mine process water ponds, and large agricultural dams.
Bladder Systems
Bladder covers operate on the same principle as a wine cask bladder — an impermeable membrane that sits on or just below the water surface, expanding and contracting with water volume. Key features include:
- Prevention of both evaporation and seepage
- Exclusion of direct rainfall entry into the storage
- Suited to purpose-built storages with controlled inflow and outflow systems
Evaporation reduction potential: Up to 85–100% depending on cover type and coverage level
4. Chemical Evaporation Suppressants
Chemical evaporation control relies on the application of a monolayer — a one-molecule-thick film of fatty alcohol or polyacrylamide (PAM) compound — on the water surface. This film reduces the energy transfer at the air-water interface, slowing the rate at which water molecules escape into the atmosphere.
Key characteristics:
- Very low initial cost compared to physical covers
- PAM and similar compounds can bind surface water molecules together, reducing evaporation
- Requires reapplication every two to four days as the monolayer degrades
- Effectiveness is significantly reduced in windy conditions, which disrupt the chemical film
- Suitable for larger storages where the per-square-metre cost of physical covers is prohibitive
Chemical methods are best treated as a budget-conscious interim solution or a supplement to other strategies, not a primary long-term fix.
Evaporation reduction potential: 10–30% (conditions dependent)
5. Biological Evaporation Control
Some aquatic plants naturally reduce evaporation by shading the water surface and disrupting wind contact. The most commonly cited examples in Australian farm dam management are:
- Duckweed (Lemna spp.) — a fast-growing floating plant that can reduce evaporation by approximately 10% when coverage is established
- Palm fronds — when placed on the water surface as a temporary floating layer, palm fronds can achieve evaporation reductions of up to 35%
Biological strategies are most appropriate as a very low-cost option for small, isolated storages where the cost of physical covers cannot be justified, or as a short-term measure while longer-term solutions are planned.
Evaporation reduction potential: 10–35%
Comparing Dam Evaporation Reduction Methods: Cost vs Effectiveness
Use this table to quickly compare the options covered in this post:
| Method | Evaporation Reduction | Upfront Cost | Maintenance |
|---|---|---|---|
| Dam Design (deeper/narrower) | 20–30% | High (earthworks) | Low |
| Windbreaks (shelterbelts) | 20–30% | Medium | Low |
| Suspended Shade Cover | Up to 90% | High | Medium |
| Continuous Floating Cover | Up to 100% | High | Medium |
| Modular / Shade Ball Cover | Up to 85% | Medium–High | Low |
| Chemical Suppressants | 10–30% | Low | High (reapplication) |
| Biological (plants) | 10–35% | Low | Low |
Key takeaway: Physical coverings offer the highest evaporation reduction — typically 85 to 100% with good coverage — and while their upfront cost is higher, they deliver the lowest cost-per-megalitre saved over time.
How EvapCo Can Help Reduce Your Dam Evaporation Losses
EvapCo is an Australian evaporation management specialist based in Port Macquarie, NSW, supplying dam cover solutions to farms, mining companies, and infrastructure projects across the country.
EvapCo’s product range includes modular shade balls and floating cover systems designed specifically for Australian conditions — from intensive horticultural operations in Queensland to large-scale mine site process water storage in Western Australia. The company’s shade ball solutions are engineered to achieve 91% surface coverage, eliminating approximately 85% of evaporation losses across a working life of ten or more years with minimal maintenance.
The economics are compelling: for a large storage losing 180 megalitres per year to evaporation with water valued at $500 per megalitre, a shade ball solution saving 150 megalitres annually generates $75,000 per year in water savings — typically outpacing the annualised installation cost within the first two years.
Ready to stop losing water? Contact EvapCo to discuss your dam’s evaporation challenge and get an assessment for your property.
Frequently Asked Questions
What is the most effective way to reduce evaporation from a dam?
Physical covers — particularly continuous floating covers and suspended shade structures — are the most effective method available. With full coverage, floating covers can reduce evaporation by up to 100%, while suspended shade covers achieve up to 90% reduction according to UniSQ research. Modular covers and shade balls, deployed incrementally, can reduce evaporation by up to 85% once full coverage is achieved.
How much water can you save with a dam cover?
The volume saved depends on your dam’s surface area, location, and the type of cover installed. In Queensland’s Granite Belt region, where evaporation rates reach 1.6 to 1.8 metres per year, a fully covered dam could retain the equivalent of 1.6 to 1.8 metres of water depth annually per square metre of surface area covered. For a one-hectare storage (10,000 m²), this represents up to 16,000–18,000 kilolitres (16–18 megalitres) of water saved per year.
Are dam covers worth the investment?
For most Australian farm and agricultural operations dealing with significant evaporation losses, yes — dam covers deliver a strong return on investment. EvapCo’s shade ball solutions for larger industrial and mining storages have demonstrated a return of $2 in water savings for every $1 invested over a ten-year product life. For smaller agricultural dams, UniSQ modelling suggests annualised costs of $700–$1,000 per megalitre of water saved for shade cloth covers — well below replacement water costs in many regions. Contact EvapCo for a site-specific cost-benefit assessment.
EvapCo is based in Port Macquarie, NSW and supplies evaporation management solutions to farms, mining companies, and infrastructure projects across Australia. For more information on the science behind evaporation, read our introduction to evaporation or our guide to estimating evaporation levels from your dam.