Australia’s rural landscape is dotted with farm dams—vital water reservoirs that underpin agricultural productivity and drought resilience.

Farm dams are essential for any agricultural strategy.

A well-planned farm dam can significantly enhance productivity.

Understanding the design of farm dams is critical.

But before you embark on the journey of building or upgrading a dam, a careful assessment is crucial.

Farm dams help manage water resources efficiently.

Farm dams provide a sustainable solution to water supply challenges.

This guide will walk you through the key considerations, calculations, and questions to determine whether a farm dam is the right investment for your property.

Understanding the Role of Farm Dams

Farm dams are more than just water storage holes in the ground. They serve as the backbone of water management for irrigation, livestock, firefighting, and even biodiversity enhancement. Their primary benefit is the ability to store rainfall during wet periods, ensuring a reliable supply during dry spells or droughts3.

Key Benefits:

Water security during droughts
Improved crop yields through controlled irrigation
Reliable water for livestock, reducing stress and health risks
Enhanced biodiversity and habitat creation
Potential for renewable energy (e.g., small-scale hydro)2 3

Step 1: Assess Your Water Needs

Investing in farm dams ensures long-term agricultural viability.

Start with a Water Audit

Before considering a dam, you need a clear picture of your property’s annual water requirements. This includes all uses—irrigation, livestock, household needs, and any other activities1 5.

Questions to Ask:

What is the total water consumption for all uses over a year?
Are there seasonal peaks in demand (e.g., summer irrigation, calving season)?
How long must your water supply last without replenishment (the “critical storage period”)—especially during drought?

How to Calculate:

List all water uses and estimate daily, weekly, and annual consumption.
Use sample tables or calculators from local authorities (e.g., WaterNSW) for livestock and crop water needs1.

Step 2: Evaluate Existing Water Sources

Farm dams can mitigate climate-related risks.

Do You Already Have Reliable Water?

A dam may not be necessary if your property has access to:

Reliable rainfall and effective rainwater harvesting
Permanent creeks, rivers, or groundwater bores
Town water supply (where available)2 5

Compare your total water demand with the average annual supply from these sources. If they can reliably meet your needs—even in drought—you may not need a dam2.

Step 3: Assess Site Suitability

Is Your Property Geographically Suitable for a Dam?

Not every property is ideal for dam construction. Assess the following:

Topography: Look for natural depressions or basins that can efficiently collect and store water2 5.
Soil Type: Impermeable soils (like clay) are best for holding water. Sandy or fractured soils may require liners or may be unsuitable.
Catchment Area: Is there enough runoff from rainfall to fill the dam? Calculate the catchment size and expected runoff2.
Flood Risk: Avoid flood-prone or highly erodible areas5.
Environmental Impact: Ensure the site is not within protected areas (e.g., Ramsar wetlands) or sensitive ecosystems2.

Professional Tip: A topographic survey can provide essential data for site selection and dam design2 5.

Step 4: Regulatory and Legal Considerations

Check Local Regulations

Farm dams are regulated to protect water resources and the environment. In NSW, for example:

You can build dams up to your Maximum Harvestable Right Dam Capacity (MHRDC) without a licence1 2.
Larger dams or those in sensitive areas require permits and environmental assessments.
There are restrictions near wetlands and other protected sites2.

Action Steps:

Visit your state water authority’s website (e.g., WaterNSW) to determine your MHRDC1.
Consult local councils or catchment management authorities for zoning and environmental requirements.

Step 5: Calculate Dam Size and Storage Needs

Critical Storage Period

Determine how long your dam needs to supply water without replenishment—often based on the longest expected dry period or drought1 2.

Evaporation Losses

Australian dams can lose up to one metre of water per year to evaporation. Factor this into your calculations: for every 4 ML of water needed, you may require a 6 ML dam to account for losses1.

Basic Formula:

Regulatory compliance is crucial when building farm dams.

Check the local guidelines for constructing farm dams.

Dam Size=Annual Water Consumption×Critical Storage Period×Evaporation AllowanceDam Size=Annual Water Consumption×Critical Storage Period×Evaporation Allowance 2

Step 6: Environmental and Operational Considerations

Wildlife and Biodiversity

Modern dam design can support local biodiversity. Shallow areas encourage fringing vegetation, which filters inflows and provides habitat1 3.

Stock Access and Fencing

Understanding the local ecosystem is vital for farm dams.

Plan for how livestock will access water. Direct access can damage dam edges and water quality. Consider fencing the dam and providing troughs with pumped water1.

Water Quality

Dams can suffer from siltation, algal blooms, and contamination. Plan for maintenance and consider the impact of farm activities on water quality5.

Map out your landscape to determine the best location for farm dams.

Step 7: Economic and Practical Benefits

Farm dams can significantly reduce irrigation costs.

Long-Term Value

A well-constructed dam can be a significant asset, increasing property value and operational resilience2 3.

Drought Resilience

With climate change increasing the frequency and severity of droughts, a dam provides insurance against water shortages, supporting both crops and livestock3.

Potential for Renewable Energy

Some farm dams can be adapted for small-scale hydroelectric systems, providing backup power in remote or bushfire-prone areas2.

Step 8: Weighing the Costs and Risks

Construction and Maintenance Costs

Dams require significant investment in earthworks, materials, and ongoing maintenance. Poorly planned dams risk failure, erosion, or water loss2 5.

Professional Input

Plan maintenance schedules for your farm dams.

Engage professionals for site assessment, soil testing, and design. This reduces the risk of costly mistakes and ensures compliance with regulations2 5.

Farm dams increase the resilience of your operations.

Step 9: Alternatives to Building a Dam

Rainwater Tanks: Effective for smaller-scale needs or where rainfall is reliable.
Bores and Wells: Useful if groundwater is accessible and of good quality.
Water Trading: In some regions, it may be possible to purchase water allocations.

Utilizing farm dams effectively can combat water scarcity.

Evaluate the potential of farm dams for energy generation.

Step 10: Making the Decision

You Need a Farm Dam If:

Consider long-term goals when planning farm dams.

Your annual water demand exceeds what current sources can reliably supply, especially in drought.
Your property has suitable topography, soils, and catchment for dam construction.
You can comply with all regulatory requirements.
The investment aligns with your long-term operational goals and risk management strategy.

You May Not Need a Dam If:

Existing water sources are reliable and sufficient.
The site is unsuitable due to soils, topography, or environmental constraints.
The cost outweighs the benefits for your scale of operation.

There are many alternatives to traditional farm dams.

Conclusion

Assessing the need for a farm dam is a multi-step process that requires honest evaluation of your water needs, property characteristics, regulatory landscape, and long-term goals. When done right, a farm dam can be a game-changing asset—delivering water security, drought resilience, and ecological benefits for decades to come1 2 3 5.

Action Checklist:

Audit your water needs
Evaluate existing sources
Assess site suitability
Check legal requirements
Calculate storage and evaporation
Consider environmental and operational factors
Weigh costs and benefits
Consult professionals

By following these steps, you’ll be well-equipped to make an informed decision about whether a farm dam is the right solution for your property.

Evaluate existing water resources before building farm dams.

Farm dams are a strategic investment for future needs.

Document the benefits of farm dams for your area.

Farm dams should be designed with sustainability in mind.

Integrate farm dams into your overall water management plan.

Farm dams are critical for maintaining agricultural operations.

How to Assess If You Need a Farm Dam on Your Property