Quick Answer: Evaporation is Australia’s largest single source of water loss from open storages — averaging 1,500–2,000 mm per year across inland NSW and Queensland. A typical 5 ML farm dam can lose 500,000–750,000 litres to evaporation every year. The only reliable way to cut that loss is to reduce the exposed surface area with covers, deepen the dam, or manage windbreaks.
Each year, Australia loses over 1.4 trillion liters of water straight up into the sky that signalizes about huge evaporation crisis we will soon face.
That’s a big figure, but what does it represent?
Why do we anticipate Evaporation Crisis?
Well, it’s equivalent to losing all the water in the Sydney Harbour – three times! Now it’s more vivid why the number is really scaring and we definitely need to do something about it. So the question of evaporation control in Australia is relevant now more than ever
If we solved this water control issue using all the possible means of evaporation reduction, we wouldn’t have a water crisis, so everything is in our hands
Key Takeaways
- Australia loses more water to evaporation than any other factor — it exceeds total rainfall in many inland regions
- A larger, shallower dam loses proportionally more to evaporation than a smaller, deeper dam with the same volume
- Floating geomembrane dam covers can cut evaporation by 70–90%; shade cloth offers only partial reduction
- Strategic windbreaks reduce evaporation by cutting wind speed across the water surface
- Managing stock access and algal growth also reduces evaporation losses by keeping the surface cleaner and cooler
Frequently Asked Questions
How much water does a typical NSW farm dam lose to evaporation per year?
In inland NSW, evaporation rates average 1,400–1,800 mm per year. A dam with 1,000 m² of surface area could lose 1,400,000–1,800,000 litres annually — more in hot summers.
Is there a practical way to measure evaporation from my dam?
A Class A evaporation pan placed near the dam gives daily readings. Multiply by a pan coefficient (typically 0.7–0.8 for open water) to estimate actual dam surface evaporation.
Does depth affect evaporation?
Indirectly yes. A deeper dam holds more volume per unit of surface area, so the percentage loss to evaporation is lower. Build deeper where your soil conditions allow.
Can windbreaks really reduce dam evaporation?
Yes — wind is the main driver of evaporation. A good shelterbelt on the windward side can reduce evaporation by 10–20% by cutting wind speed across the water surface.
Need help with your own dam? Book a site inspection with Big Ditch — we build and repair dams across NSW, Queensland, and Victoria.
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