What you see
Slow, steady drop during hot windy weather
More likely cause: evaporation.
Check next: compare the loss with nearby dams and recent weather.
Dam evaporation & water loss diagnosis
Dam Evaporation Control and Water Loss Management
If your dam is dropping, the first job is working out whether the water is evaporating, leaking, seeping through the wall, or escaping through a pipe or spillway problem.
Short answer: Dam evaporation control starts with diagnosis. In hot, dry or windy weather, evaporation can remove a surprising amount of water, but wet patches below the wall, fast water drops, sinkholes or green strips often mean leakage. Big Ditch checks the cause before recommending shade balls, floating covers, wind protection, dam sealing, repair or rebuild work.
Is your dam leaking or evaporating?
What you see
Wet patch or green strip below the wall
More likely cause: leak or seepage.
Check next: inspect the toe, wall and downstream area.
What you see
Fast drop after filling
More likely cause: leak path, poor clay or pipe issue.
Check next: check old pipework, rock seams and wall compaction.
What you see
Water loss plus sinkholes or soft spots
More likely cause: internal erosion or piping.
Check next: stop guessing and get the dam inspected.
Evaporation control options
Shade balls or evaporation balls
Useful where surface exposure is the main issue and the dam shape suits a floating cover approach.
Floating covers
Can reduce direct sun and wind contact, but need the right installation and maintenance plan.
Wind protection
Windbreaks and edge planting can reduce surface disturbance on suitable sites.
Dam shape and depth
Shallow dams lose more water. A deeper, better-shaped storage can reduce evaporation pressure.
Leak repair
If the problem is seepage, evaporation products will not fix the real cause.
Water-use planning
Sometimes the right answer is storage design, pumping schedule or extra capacity.
Dam evaporation help across NSW, Queensland and Victoria
Big Ditch helps landowners diagnose dam water loss across New South Wales, Queensland and Victoria, including projects around Sydney, Brisbane, Melbourne, the Northern Rivers and surrounding rural regions. The right evaporation-control option depends on the dam surface area, wind exposure, shade, depth, water use, access and whether the dam is actually leaking.
If the water loss is not normal evaporation, the next step may be dam sealing and leak repair, dam repair contractors or a broader dam maintenance plan.
How to estimate whether your dam loss is normal evaporation
The Bureau of Meteorology publishes average monthly and annual evaporation maps for Australia using Class A pan evaporation. Those maps are useful for checking whether a dam is losing water in line with local climate conditions, because evaporation depends on cloudiness, air temperature and wind speed.
Simple rule of thumb: 1 millimetre of evaporation over 1 square metre of water surface is about 1 litre of water. Multiply the dam surface area by the daily evaporation depth in millimetres to estimate daily water loss.
For example, a dam with a 1,000 square metre surface area loses about 1,000 litres for every 1 millimetre of evaporation. If the measured loss is much higher than local evaporation conditions explain, the dam may also be leaking through the wall, floor, pipework or spillway.
Cost, timing and seasonality
What affects evaporation-control cost?
Cost depends on dam size, surface area, access, wind exposure, product choice, installation method and whether the real issue is evaporation, leakage or both. Big Ditch recommends diagnosing the cause of water loss before buying shade balls, covers or repair products.
How long does a water-loss inspection take?
Inspection timing depends on access, dam size, site conditions and the amount of investigation needed. The aim is to separate normal evaporation from leaks, pipe problems, spillway issues, poor clay or structural faults before recommending a control method.
When should evaporation control be planned?
Evaporation pressure is usually highest in hot, windy periods, so planning before summer is ideal. If water levels are already low, it can also be a good time to inspect the wall, floor, pipework and spillway while problem areas are more visible.
Do not buy evaporation gear until the cause is clear
If the dam is leaking through the wall or pipework, a cover or shade-ball system can waste money. Diagnose the water loss first.
When evaporation control is not enough
Evaporation management helps when the main problem is weather exposure. It is not a substitute for dam sealing, wall compaction, pipe repair or rebuilding a failed section of dam.
Field note: A dam can be evaporating and leaking at the same time. The practical question is which loss is costing you the most water and which fix will actually work.
Related Big Ditch services
Frequently asked questions
How do I know if my dam is losing water to evaporation?
Compare the rate of loss with nearby dams, recent weather and local evaporation conditions. A slow, steady drop during hot and windy weather can be normal evaporation. Wet patches below the wall, sinkholes, pipe leaks or sudden drops may point to leakage instead.
How much water can a farm dam lose to evaporation?
Water loss depends on surface area and local conditions. As a simple estimate, 1 millimetre of evaporation over 1 square metre of water surface is about 1 litre of water. Larger, shallower dams can lose substantial volumes because they expose more surface area.
How do I calculate daily evaporation loss?
Multiply the dam surface area in square metres by the evaporation depth in millimetres. For example, 1,000 square metres of surface area losing 1 millimetre of water equals about 1,000 litres of water loss.
Do shade balls stop all evaporation?
No. Shade balls reduce sun and wind exposure on the water surface, but they do not stop all evaporation and they will not fix a leaking wall, floor, pipe or spillway.
Are floating covers better than shade balls?
Floating covers and shade balls suit different sites. The better option depends on dam size, access, wind, maintenance, budget, water quality needs and whether the dam is used by livestock, pumps or irrigation systems.
When is the best time of year to treat dam evaporation?
Planning before the hottest and windiest months is usually best. Low-water periods can also be useful because the wall, floor, pipework and spillway are easier to inspect for leaks or structural problems.
Can Big Ditch check whether my dam is leaking?
Yes. Big Ditch can inspect the dam, wall, toe, pipework, spillway, water-loss pattern and site conditions to help determine whether the problem is evaporation, leakage or both.
Do I need approval to install a floating cover or modify a dam?
Approval requirements depend on location, dam size, waterway impact and the type of work proposed. Landowners should check the relevant NSW, Queensland or Victorian requirements before major dam works or modifications.
Does Big Ditch work in NSW, Queensland and Victoria?
Yes. Big Ditch works with landowners across New South Wales, Queensland and Victoria, including projects around Sydney, Brisbane, Melbourne, the Northern Rivers and surrounding rural regions.
What is the first step if my dam is losing too much water?
Start by identifying whether the loss is normal evaporation, high evaporation caused by exposure, or leakage through the dam structure. Once the cause is clear, Big Ditch can recommend the most practical next step.
Get the cause of water loss checked
Tell us how quickly the dam is dropping, what the weather has been doing, and whether you can see wet areas below the wall.