Quick Answer: A farm dam needs to be inspected at least twice a year — once before winter and once after summer. The key things to check are the dam wall for cracks or settlement, the spillway for blockages or erosion, the inlet and outlet pipes, and the water level. Catching small problems early is always cheaper than fixing them after they’ve become big ones.
Nobody Tells You This When You Buy Rural Land
When you take on a property with a dam — or build a new one — the focus is almost entirely on construction. Getting the water in. Getting the size right. But once the excavator drives away, most first-time dam owners are left with a question nobody warned them about: now what?
The good news is that a well-built earth dam doesn’t need much. It’s not like a pump or a trough that needs constant attention. But it does need regular eyes on it, and knowing what to look for makes all the difference. This checklist is designed for people who are new to dam ownership — no engineering background required.
How Often Should You Inspect a Farm Dam?
Twice a year is the minimum. The best times are:
- End of summer (February–March) — after the hottest, driest period when evaporation is highest and the dam is under the most stress from low water levels and cracking
- End of winter (August–September) — after the wet season, when you can see how the dam handled full water levels and any significant rainfall events
If you’ve had an unusually heavy rain event, a flood, or you’ve noticed anything odd with the water level, do an extra check straight away. It only takes twenty minutes to walk the dam properly — and it’s time well spent.
The Dam Wall: What to Look For
The dam wall (also called the embankment) is the most critical part of the whole structure. This is where most problems start.
Walk the Entire Crest and Both Faces
Don’t just look at the dam from a distance. Walk the top of the wall from one end to the other, then walk around the downstream face (the side that faces away from the water). You’re looking for:
- Cracks — any cracks running along the top of the wall or across it are worth taking seriously. Small surface cracks from drying out are usually harmless. Cracks that run deep or that have grown since your last inspection need a professional look.
- Settlement or depressions — if part of the wall looks lower than it used to, or there’s a dip or hollow in the crest, that’s a sign of uneven settlement which can create a weakness.
- Wet patches or seepage — the downstream face of the wall should be dry. If you see wet ground, weeping water, or unusually green grass at the base of the wall on the downstream side, water is moving through the embankment. This needs attention.
- Animal burrows — wombats, rabbits, and even foxes will burrow into dam walls. Walk slowly and look carefully for any holes, especially on the upstream face where you can’t always see from a distance.
- Stock damage — cattle and sheep congregating near the water’s edge will erode the upstream face over time. Poaching (deep hoof marks in soft soil) weakens the wall structure.
The Spillway: Your Dam’s Safety Valve
The spillway is the channel that lets excess water escape safely when the dam is full and it’s still raining. If it fails or blocks, the dam can overtop — and an overtopping dam can wash out the wall in hours.
Check for:
- Vegetation overgrowth — trees and dense shrubs growing in or near the spillway will restrict flow and their roots can undermine the structure. Keep it clear.
- Erosion channels — if the spillway has been used recently (after a rain event), check whether the flow has scoured any channels or undermined the edges. Small erosion channels can grow quickly once they start.
- Debris blockages — branches, rubbish, and sediment can partially block a spillway. Clear anything that could restrict flow during a flood event.
- Rock or concrete protection — if your spillway has rock armouring or concrete lining, check it’s still intact and nothing has shifted or been displaced.
Inlet and Outlet Pipes: Small Parts, Big Problems
Not all dams have pipes, but if yours does — a trickle tube, a standpipe, or a stock water supply pipe — they need checking too.
- Check for leaks around the pipe entry point — where a pipe passes through the dam wall is always a potential weak point. Look for wet ground or seepage around the pipe on the downstream side.
- Check that inlet screens or trash racks are clear — if the inlet is blocked, you lose the ability to draw down the dam level in an emergency.
- Check valves and gates operate freely — if you haven’t operated the valve in twelve months, do it now. A valve that seizes shut when you need it is a serious problem.
Water Level and Water Quality
Keep a simple record of the water level each time you inspect. A physical marker — a star picket with painted depth marks on the upstream face — costs almost nothing and gives you a reference point over time. If the level is dropping faster than seasonal evaporation can explain, you have a leak to investigate.
On water quality, look for:
- Algae blooms — blue-green algae (cyanobacteria) is toxic to stock and pets. It looks like blue-green paint or scum on the surface. Don’t let animals drink from an affected dam.
- Unusual colour or smell — dark, murky water with a strong odour can indicate decomposing organic matter or high nutrient levels.
- Dead fish or stock avoiding the water — both are warning signs worth investigating.
Your Seasonal Maintenance Summary
| Season | Key Tasks |
|---|---|
| Summer (Dec–Feb) | Monitor water level weekly, watch for algae blooms, keep stock away from wall edges |
| End of Summer (Feb–Mar) | Full inspection: wall, spillway, pipes, water level record. Check for drying cracks in wall. |
| Winter (Jun–Aug) | Check spillway is clear before the wet season. Operate any valves or gates. |
| End of Winter (Aug–Sep) | Full inspection: check how dam handled rainfall. Look for erosion, seepage, wall movement. |
| After any major rain event | Walk spillway and downstream wall face. Check for new erosion or scour channels. |
When to Call a Professional
Most of what’s on this checklist is observation — you’re the eyes on the ground and you don’t need any qualifications to do it well. But if you find any of the following, get a dam builder out to assess before it becomes an expensive problem:
- Seepage or wet ground on the downstream face of the wall
- Cracks that run deep, have grown, or run across the wall (not just along the surface)
- A water level that’s consistently dropping faster than evaporation explains
- Any sign of animal burrows through the embankment
- Significant erosion in the spillway
- A valve or pipe that won’t operate properly
Big Ditch offers paid site inspections across NSW from $500. It’s the fastest way to get a straight answer on whether what you’ve found is something to worry about — or not.
Key Takeaways
- Inspect your dam at least twice a year — end of summer and end of winter
- Walk the full crest and downstream face of the wall every inspection
- The spillway must be kept clear of vegetation and debris at all times
- Keep a simple water level record so you can spot unexpected drops
- Seepage on the downstream wall face, deep cracks, and animal burrows all need professional assessment
Frequently Asked Questions
How often should a farm dam be professionally inspected?
For most rural farm dams, a professional inspection every 5–10 years is reasonable, combined with your own regular checks. Larger dams, dams that have had problems, or dams used for critical water supply should be assessed more frequently.
What does normal cracking in a dam wall look like?
Shallow surface cracks running along the top of the wall in dry weather are usually just the result of the soil drying out and are not a structural concern. Deep cracks, cracks that run across the wall, or cracks near the spillway junction are more serious and worth getting looked at.
How do I stop stock from damaging the dam wall?
Fence the dam wall and restrict stock access to a specific drinking point — ideally a hardened or gravelled ramp on the upstream face at one end. This protects the wall from poaching (hoof damage) and keeps the water cleaner.
Is blue-green algae dangerous to cattle?
Yes — some strains of blue-green algae (cyanobacteria) produce toxins that can kill cattle, sheep, horses, dogs, and other animals quickly. If you see a blue-green scum or paint-like film on your dam surface, fence it off and contact your local vet or DPI office for advice.
Can Big Ditch inspect my dam for me?
Yes. We carry out paid site inspections across NSW and can assess the condition of your dam wall, spillway, and pipes. Book an inspection here — it’s the best $500 you’ll spend on your water infrastructure.
Not sure what to look for on your dam? Book a site inspection with Big Ditch and we’ll give you a full condition report.