Dam Management Fundamentals for Healthy Irrigation Water
Q. We are having trouble with weeds/algae which are blocking the foot valves of our pumps. We have treated and now have got rid of algae and most of the weed. Can you please provide advice on treating our dams moving forward?
ANSWER
Dam Management Fundamentals for Healthy Irrigation Water
Effective dam management is about more than just water storage — it’s about maintaining a stable aquatic environment that supports consistent irrigation performance and reduces issues like algae growth and pump blockages. Below are key areas and practical treatment options to help keep your dam in balance.
1. Maintain Stable Water Levels
One of the most important areas in dam management is consistency.
Where possible, avoid large fluctuations in water levels. Letting a dam drop significantly and then refilling it in one large volume creates instability in water chemistry, as the system has to repeatedly rebalance.
A better approach is to pump in water as you pump out, maintaining steady turnover. This helps:
- Stabilise water chemistry
- Reduce biological stress
- Support a healthier aquatic environment overall
2. Understand Volume vs Surface Area
Most dams are bowl-shaped, meaning changes in water level significantly impact system behaviour.
When water levels are kept high:
- The dam holds more volume relative to surface area
- Solar energy is distributed through more water
- Heat stress is reduced
This results in:
- Lower water temperatures
- Improved biological stability
- Reduced algae and aquatic plant growth
Higher and more stable water levels create a more resilient system.
3. Correct Irrigation Draw Point Placement
Water quality entering your irrigation system depends heavily on where the foot valve is positioned.
Most organic matter (including algae) is found:
- In the top 1 metre of water
- In the bottom 0.5 metres of water
To minimise debris intake, the ideal draw point is:
- Approximately one-third down from the water surface
Additional best practices:
- Position the foot valve in the centre of the dam
- Avoid placing it near the edges
- Keep it away from prevailing wind direction
Poor placement can significantly increase organic load and lead to pump clogging and filtration issues.
Common Dam Management Treatments
A. Aeration
Aeration is one of the most effective long-term tools for improving water quality and stabilising dam ecosystems.
Surface Aeration (Smaller Dams)
Surface fountains help circulate and oxygenate water.
The Evolution Half HP Fountain is suitable for water bodies up to approximately 2,050 sqm and is a strong entry-level solution. More information and see a video of this in action.
Subsurface Aeration (Larger Dams)
For larger systems, lake bed aeration can be more effective.
The Air Pro 1 Diffuser system delivers oxygen directly at depth, with each diffuser pod covering up to 3,000 sqm of surface area. More information.
B. Algae Control
For irrigation dams, Coptrol is a recommended algaecide.
Application rates:
- 5 L per megalitre (volume-based dosing)
- 8.4 L per 1,000 sqm (surface-area dosing)
Watch Coptrol how to videos here.
C. Algae and Aquatic Plant Suppression
Aquatic Blue works by tinting the water, reducing light penetration and limiting photosynthesis. This helps suppress both algae and aquatic plant growth over time.
Watch Aquatic Blue how to video here.
Stable water levels, correct pump placement, and a combination of aeration and targeted treatments all work together to create a healthier, more manageable dam system. The goal is not just control, but long-term stability of the water biology.
