Introduction
Water is the most important thing for any farm, and a well-placed farm dam can keep your water safe for decades.
I’ve been building and designing dams for more than 30 years, and I can tell you that choosing the right site is the most important thing you can do when building a new dam.
If you pick the wrong site, it could cost you a lot of money, cause problems with upkeep, and even hurt the environment. On the other hand, a well-chosen site will give you reliable, high-quality water with little work on your part.
When considering the best site for your farm dam, various factors come into play such as the topography and soil quality. Before proceeding, always assess the conditions that affect the best site for your farm dam. Implementing the right strategies to determine the best site for your farm dam will maximize efficiency and sustainability.
This detailed guide will help you choose the best site for your farm dam by using decades of real-world experience and the most up-to-date technical advice.
Understanding What Site Selection Means
The location you pick for your dam will decide:
- How much water you can keep for a certain amount of money
- The quality and dependability of that water
- The dam’s long-term stability and upkeep needs
- The effect on the environment of your property and the land that comes after it
- Your compliance with laws and rules
- The carrying capacity of the site is important when identifying the best site for your farm dam.
- You can minimize potential risks by thoroughly analyzing the best site for your farm dam before construction.
- Understanding the best site for your farm dam is essential for ensuring long-term success in water management.
- The best site for your farm dam should be a collaborative decision based on insights from multiple stakeholders.
- Ultimately, the best site for your farm dam hinges on careful planning and execution of your design.
- Consider the long-term implications when determining the best site for your farm dam
- Choosing the best site for your farm dam requires thorough research and planning.
- The best site for your farm dam will ensure a sustainable water source for years to come.
- Site assessments should always take into account the potential for identifying the best site for your farm dam
- Evaluate your options carefully to ascertain the best site for your farm dam that meets all requirements.
- Factors to consider for the best site for your farm dam include environmental impacts and legal regulations.
- Accessibility considerations are key when determining the best site for your farm dam
- Evaluate the health of your catchment area to determine the best site for your farm dam
- Proximity to water usage areas influences the choice of the best site for your farm dam
Let’s look at the most important things you need to think about.
1. Topography: Use the Land to Your Advantage, Not Against It
Natural Depressions and Gullies
Drainage patterns should be considered when assessing the best site for your farm dam.
A natural gully or depression with sides that slope down gently is the best place for a dam. This lets you get the most storage space with the least amount of digging, which saves money and doesn’t disturb the environment as much. A narrow gully that gets wider as it goes upstream is often the best choice because it has a high storage-to-excavation ratio. This means that you can store more water for every cubic metre of earth you move.
Slope Considerations for Finding the Best Site for your Farm Dam
Stay away from places where the slope is more than 15%. Steep slopes not only make building more expensive, but they also make it hard to find enough good material for the dam wall and can make it less stable. Building on flatter land is easier and less expensive, but you still need enough natural fall for water to flow into the dam.
Area of Catchment
Your dam needs a catchment area that can reliably fill it. A 5-hectare catchment with a moderate slope is usually enough to fill a small dam (up to 1,000 cubic meters) in coastal areas. However, this can change depending on the type of soil and how much it rains. Use topographic maps and surveys of the land to figure out where water naturally flows and collects on your property.
2. The Type of Soil and the Geology: Foundations of a Good Dam
Ability to Hold Water
The soil under and around the dam is what makes it so good at holding water. The ideal soils for building a dam have 40 to 60 percent sand, 10 to 20 percent silt and 20 to 40 percent clay. The most important part is the clay, which expands when wet to seal the dam tight and stop seepage.
Testing the Soil
Don’t ever forget to check your soil. Do a series of soil tests, like the ribbon test and the permeability test, to see if your site has enough material that won’t let water through. Stay away from places with sand, gravel, or broken rock unless you’re ready to spend a lot more money and do a lot more work.
Borrow Pits
You will need to find some good clay close by to build the dam wall. The excavation for the dam itself should give you enough material, but sometimes you’ll need to find a different borrow area.
3. Managing the Source of Water and the Catchment Area
Reliable Inflow
Check how reliable your water source is. Is it water that runs off the ground, a creek, or groundwater? Look at how rain falls and how it has flowed in the past. A dam is only as good as the water that flows into it. If there isn’t enough water, the dam will be empty; if there is too much, it could overflow and cause erosion.
Health of the Catchment
Dams are healthy when their catchments are healthy. To stop erosion and filter runoff, keep at least 80% of the ground in the catchment zone covered with perennial grasses. To keep the water quality good, don’t put your dam below places where a lot of nutrients or chemicals run off, like stockyards or fertilised paddocks.
4. Storage-to-Excavation Ratio: Getting the Most Out of Your Earthworks
The storage-to-excavation ratio is an important number because it shows you how much water you can store for every cubic metre of earth you move. A ratio higher than 1:1 is best, and a gully with a gentle slope upstream and a narrow outlet will give you the best results.
Make It Fit Your Needs
Don’t build too much. Make sure the dam can hold enough water for your needs, whether it’s for irrigation, livestock, or home use, plus a little extra for dry years. Too big dams cost a lot of money and might be harder to fill, while too small dams might not be able to meet your needs in a drought.
5. Environmental and Biodiversity Considerations: Reducing Impact
If a dam is built in the wrong place, it can cause erosion, change the flow of water, and hurt delicate habitats. Don’t build on waterways that are important for the environment or in places where the dam will bother people or wildlife downstream.
Engage with professionals to help identify the best site for your farm dam and adhere to legal standards.
Helping Biodiversity
Dams that are well-planned can help farms become more diverse. Think about places where you may link the dam to shelterbelts or leftover plants to make habitat corridors for native animals. Make the dam’s edges shallow so that aquatic plants can grow and the water that comes in can be filtered.
6. Access and Infrastructure
Close to Use
To keep pumping and piping costs down, place your dam as close as possible to where the water will be used, like stock troughs, irrigation systems, or homes. But you also need to think about the need for good soil and a good catchment.
Consideration of environmental factors is essential when determining the best site for your farm dam.
Access to Stock and Vehicles
Make sure that livestock and vehicles can get in and out safely and in a controlled way. To keep erosion and damage from happening, hardened access points should be far away from the dam wall and spillway.
7. Managing the Spillway and Overflow
Safe Overflow
Every detail matters when selecting the best site for your farm dam, particularly regarding the spillway design.
To safely deal with extra water during storms, every dam needs a well-designed spillway or bywash. The spillway should send water back to the natural flowline without causing flooding or erosion on properties downstream.
Suitability of the Site
Pick a spot where the ground below the dam is stable and can handle overflow without hurting the environment or infrastructure.
8. Following the Law and Regulations
Getting Permits and Approvals
Every state in Australia has rules about farm dams. You might need development consent, water extraction licenses, or environmental approvals, especially for bigger dams or those that are on rivers. Before you start working, always check with your local council and water authority.
Regulatory compliance is crucial in selecting the best site for your farm dam to avoid legal issues.
Responsibility of Care
You are in charge of making sure the dam is safe, doesn’t hurt anyone else, and follows all the rules that apply to it. Hire qualified engineers to help with design and construction when needed.
9. Cost and Usefulness
Make a Realistic Budget
The biggest costs are for earthworks, supplies, and getting the site ready. If the site is steep, rocky, or has bad soil, it could cost you twice or three times as much. If the site is marginal, think about the ongoing maintenance and possible repair costs.
A Long-Term View
A dam that is built in the right place is an investment that pays off for decades. If you cut corners when choosing a site, it could cost you a lot of money or cause problems that never go away.
10. Professional Help and Advice
Get experienced dam builders, engineers, and hydrologists involved early on. Their knowledge may help you avoid frequent mistakes, make your design better, and make sure it meets all the rules.
Government and Community Resources
Use the resources of local water agencies, catchment management authorities, and agricultural extension services. A lot of them give free or low-cost advice and technical guides. Consider the community and environmental impacts when selecting the best site for your farm dam.
Step-by-Step Checklist for Choosing a Site
- Make a map of your property: Find all the natural depressions, gullies, and possible catchment areas.
- Use contour maps or a topographic survey to look at the slopes and drainage patterns of the land.
- Test the Soils: Do soil tests at the proposed site and any possible borrow areas.
- Estimate Catchment Yield: Figure out how much water will likely flow in based on the size of the catchment and the amount of rain that falls.
- Check Proximity: Make sure the site is close enough to where the water will be used.
- Check the Environmental Impact: Stay away from sensitive areas and limit the effects on the water downstream.
- Plan for the Spillway: Make sure there is a safe, stable way for water to overflow.
- Talk to the authorities: Find out what rules you need to follow and get the right permits.
- Get estimates and include all costs when making a budget for building and upkeep.
- Get Professional Help: Hire professionals to oversee the design and construction.
Common Mistakes to Avoid
- Building on sandy, rocky, or very permeable soils without proper engineering
- Not realising how big the catchment area needs to be to fill the dam
- Putting the dam too far away from where water is needed, which raises costs
- Not paying attention to the need for a safe, stable spillway
- Not checking to see if you meet legal and environmental criteria
- Not thinking about how the dam will affect people and ecosystems downstream
Conclusion
Picking the best spot for your farm dam is hard but worth it. If you think carefully about the land, soil, water supply, environmental effects, and legal requirements, you can build a dam that will last for generations on your farm. Keep this in mind: the dam that costs the least is the one you only have to build once. If you’re not sure, get help from a professional. A little bit of planning and site assessment can save you a lot of money and headaches in the long run.
Further reading
Understanding the long-term benefits of choosing the best site for your farm dam for optimal sustainability. These resources will aid in determining the best site for your farm dam.
1. Building a farm dam – NSW Environment
https://www.environment.nsw.gov.au/publications/building-farm-dam
2. Farm Dams Technical Guide – Sustainable Farms
https://www.sustainablefarms.org.au/resources/farm-dams-technical-guide/
3. Farm Dam Construction in Rocky Terrain – Big Ditch
https://www.bigditch.com.au/farm-dam-construction-in-rocky-terrain/
4. Farm-scale dam design and costs – CSIRO
https://www.csiro.au/~/media/Major-initiatives/Northern-Australia/NAWRA-technical-reports/NAWRA-Technical-Report—Farm-dam-design_LO-RES.pdf
5. Farm Dam Handbook – WaterNSW
https://www.waternsw.com.au/documents/publications/education/FarmDamFinalLR.pdf
6. Enhancing farm dams – Sustainable Farms
https://www.sustainablefarms.org.au/wp-content/uploads/2023/05/Enhancing-Farm-Dams-guide.pdf
7. Farm dams – Department for Environment and Water (SA)
https://cdn.environment.sa.gov.au/landscape/docs/ny/201211_dams_fact_sheet.pdf
8. Planning a new farm dam – Sustainable Farms
https://www.sustainablefarms.org.au/wp-content/uploads/2023/02/Farm-dams-technical-guide-PDF_Section-3.pdf
9. Farm Dam Construction: Key Planning & Design Factors – Big Ditch
https://www.bigditch.com.au/farm-dam-construction-in-rocky-terrain/
10. Beginner’s Guide to Building a Farm Dam on Your Property – Big Ditch
No direct link found in the search results. This may require a manual search on the Big Ditch website or similar sources.
11. Farm Dams – A Guide to Siting, Design, Construction – Sheep Connect SA
https://www.sheepconnectsa.com.au/downloads/farm-dams-fact.pdf