This page is about earth dam construction for water retention purposes. Building a small to medium-scale earth dam like the ones described on this page can provide water for irrigation, aquaculture, recreation, ecosystem restoration, and other uses. Note, we’re not experts in earth dam design. We’ve just done an immense amount of research on the topic after identifying a need for earth dams as part of the open source One Community Highest Good Housing and Food components.
We share all we’ve learned with the following sections:
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Earth dam construction is a viable option in many places for water storage and pond or lake creation. Systems will vary from place to place, so design of your water storage feature warrants flexibility and careful observation of the surrounding landscape. The ideal solution is one that maximizes water storage and minimizes human intervention. This can be accomplished by mindfully educating ourselves on the natural elements we are working with.
The earth dam construction content here is from hours of research on this topic. Our goal is to organize what we’ve learned into some broad guidelines and hopefully turn a nebulous and daunting task into a viable water-retention solution. The overall steps of the process are outlined in the flowchart below.
Dams encircle the lower perimeter of where water wants to flow to create ponds that are replenished by both surface runoff and subsurface flow. Although water tanks are preferred for drinking water, they can cost 100x more for the same amount of water stored in an earth dam. The ponds and lakes created by small earth dams also develop valuable wetland ecosystems, beautiful recreation areas, aquaculture options, and large-scale water storage for emergency and/or agricultural use. Small DIY earth dams minimize flooding during the wet season, keep water from drying up during the dry season, combat erosion, and allow the standing water behind the earth dam to better percolate into the ground, recharging the groundwater and raising the water table.
Our goal with this page is to share everything our research has taught us about DIY earth dam construction. There are many different types of earth dams that you can construct, but the basics of construction are the same. The image below shows the most common earth dams and we use the following sections to discuss each of these (and others) and the ways to build them:
You must be aware of and adhere to local laws before constructing an earth dam. Failure to do this can lead to forced removal of your construction. Plan ahead for this because meeting with the local watermaster, local county authority for land use permitting, fish and wildlife services, and/or the state for permission can take 6 months or more
Depending on the size and location of your earth dam, you may also need to enroll a civil and/or structural engineer in the design process. Here are a few of the things to think about:
These and any other safety concerns need to be thought of and addressed from the beginning.
It’s a scary business, it’s scary designing, especially when a lot of dirt’s been moved and sheets of water are spreading across the landscape. That’s scary. And if it scares you too much, get someone in to do it.
~ Bill Mollison ~
Typically, 1.6 to 3 feet (0.5 to 1.0 meter) of clay is needed to seal an earth dam. The pond water level naturally fluctuates, resulting in periodic wetting and drying of the pond bed. When the bed is exposed and not submerged under water, the clay layer can crack as it dries and these cracks can go down about 1.6 feet (0.5 meters), so 3 feet (1 meter) is ideal to account for this natural cyclical process.
When enough clay is not available at the site of the pond, we must consider other alternatives to seal the pond bed. The benefits of having a pond for water storage outweighs the use of non-natural materials that may be needed. If a pond is leaking, these methods can be tried – ideally in this order for minimum effort:
There are many different types of earth dams you can construct. This table shows the most common types.
Here are all the good locations we could find for each of the above using a topo map, Google Earth, and 1-square-mile parcel of land.
We explore each of these (and a few others) with additional notes and more specific imagery below.
Valley earth dams are constructed across a valley or gully. These dams, sometimes called a “barrier dam,” are most frequently used as energy systems. Especially when built in the path of a flowing or intermittent stream bed. These dams are also valuable for storing large volumes of water, as well as for irrigation. For these dams, it is particularly important to over design the spillway and accommodate any fish passage that has been obstructed due to dam installation.
Ridgepoint earth dams are located on flattened portions of descending ridges and are quite rare. It is composed of a single, horseshoe-shaped wall. These dams are most useful for water storage and runoff collection.
Keypoint earth dams are located in lower country where hills transition from convex to concave. These dams are primarily used to store irrigation water and are amenable to being placed in series on descending contours. These are most appropriate for 4-12% slopes.
Contour earth dams are located along hillsides where the contour widens on relatively flat terrain (slope of 8 percent or less). They are 3-sided and the front of the dam is either concave or convex to follow the contour. They are most useful for domestic livestock and aquaculture. These tend to be relatively expensive in comparison to their water storage capacity. Like keypoint dams, contour dams are amenable to being placed in series on descending contours. There is insufficient natural catchment so diversion channels or swales are essential.
Turkey nest earth dams are earthen water storage tanks best placed on the highest available site with flat ground. These dams do not capture runoff, so they must be filled with external water sources. These are much cheaper than constructed tanks, but limited to use for irrigation, where as constructed tanks can be used for drinking water as well. These dams should be at least 100 feet x 100 feet x 10 feet (providing approximately 0.6 million gallons of storage) to be cost effective.
Saddle earth dams are unusual because this type of land feature is rare – a saddle between two hills. These dams have two walls. These dams are most useful for fire control and ecosystem/wildlife support. This type of dam typically ends up being the highest dam on the landscape and has the potential to fill from hill runoff.
A barrage earth dam is one of the least likely DIY dams you’d probably consider constructing. This is because they incorporate a large mechanical component to control gates that regulate the amount of water they store. Barrage dams are normally built near the mouth of the river and used to divert water for irrigation needs or limit the amount of water going down-stream. Water builds up behind these dams and a number of large gates are opened or closed to control the amount of water passing through. This allows the structure to regulate down-stream water while also stabilizing river water elevation upstream for use in irrigation and other systems.
Here’s a video about these commonly commercial-scale dams. It provides a good explanation of the difference in function between a traditional dam and a barrage dam.
Here we discuss the steps for constructing your own earth dam. Again, we’re not experts in earth dam design or construction. We’ve just done an immense amount of research on the topic after identifying a need for earth dams as part of the open source One Community Highest Good Housing and Food components. We share here all we’ve learned with the following sections:
Throughout the life of the project, engage in a dynamic thinking process and be flexible and receptive, allowing nature to be your guide. During the planning stage it is important to clearly define the purpose and overall desired outcomes of the project and identify the resources available. Include in your resource evaluation your financial resources, your equipment resources, the lay of the land, and personal and local knowledge base.
When working with nature, it is imperative to have a variety of applications that serve the same or similar end uses. With a water retention landscape, it is wise to have a mixture of earth dam types to meet your end-use needs. This is safer and usually easier. It also better prepares you for unpredictable natural events, such as seasonal and intraseasonal extreme weather variations. To select the appropriate number and types of earth dams, the following table can be utilized:
Here are some additional guidelines:
It is crucial to have soil with sufficient clay content for the earth dam structure, as well as the pond bottom. Soil with at least 40 percent clay is necessary to build a water-tight earth dam, and to retain water in the pond. Given the importance of this criteria, it is worth the money to rent an excavator to dig and evaluate the soil at the potential earth dam sites identified in the step above. The “Taking Test Slices” section below discusses how to do this.
Use models and small experiments to more deeply understand the local landscape’s potential for water storage. It is very hard to work with free-draining soil (deep or coarse sands), rocky areas, and/or areas too steep or unstable. The bottom of gentle slopes are usually better choices.
If clay has to be brought in (versus mined on your own property), rethink the pond location and/or water storage method.
Taking test slices helps you understand the types of soil you will be dealing with. Using an excavator (if available), assess the geology 6 to 12 feet below the ground surface at around 6 different locations. You can go as deep as 15 feet, but beyond that returns diminish. Dig until an impermeable layer is reached near the depth you want your pond to be. This article called “soil permeability” explains well what you are looking for and why.
The geology can be significantly different just 30 feet away. In some areas it is helpful to have the excavator put each scoop in sequence so each layer can be assessed for clay content. The excavated materials (called the “overburden”) may need to be sorted to arrive at the correct clay content. Forty percent clay or more is the goal. If you don’t have 40 percent or more clay, another area on the property may need to be mined. The video below shows how to test and measure your clay content.
Note: For earth dam construction, it is preferable to use test slices over coring. This is because coring typically only provides an assessment for the first 3 feet below the ground surface and you are seeking to assess your soil between the depths of 6 and 15 feet.
Earth dams may not be the ideal solution for all locations and there are many different kinds of earth dams (see “Types Of Dams” above). Here are the key guidelines our research identified:
Sepp Holzer uses a water-retention-landscape style where the surrounding forest is your water reservoir. Water from your dammed area spreads through the surrounding ground and helps develop a lush landscape. The picture and video below are about one of Sepp’s earth dams and the landscape like this that he created.
A successful water retention landscape can be created using basic principles and well-established parameters. At a minimum, a water retention landscape is comprised of earth dams, embankment ponds, spillways, and erosion control interventions. On some landscapes, sediment traps, diversion drains, and swales make sense. In simple terms, assure that the local soil has at least 40 percent clay, all earth dam walls can be less than 20 feet (6 meters) high and still meet minimum volume/end-use requirements, and that the pond length behind the earth dam is at least 3 times longer than that earth dam’s length. An expanded array of details is provided in the image and text below:
Below are our notes taken regarding the main features shown in the image above:
“Wherever you are doing earthworks, you need to carefully remove the topsoil and not conglomerate topsoils and subsoils together. It’s taken 100s or 1000s of years to make that topsoil, you’re not going to make it again too easy. Separate it and then make your shapes and forms.”
~ Geoff Lawton ~
For dessert landscapes, have your silt (or sediment) trap above the main water feature.
You can put in other attachments too. Examples are swales (tree-growing systems), ledges for plants, and/or deep-water refuge for fish in areas where water freezes.
Wherever you are in the business of making swales, work out how big they aught to be, then triple it. If they’re going to be a meter wide and a meter deep, make them 3 meters – 4 meters wide, and 3 meters deep and you might hold those big events. But if you don’t, it’ll blow the lot out. If your top swale blows, then the bank goes, and all your other swales go.
~ Bill Mollison ~
Two case studies are presented below from work completed by Geoff Lawton. These are from the Permaculture Design Course DVDs where he taught with Bill Mollison. One key takeaway from both is placing emphasis on making things very level, so water flows will soak passively and carry nutrients around the property. We’ll add our own case studies here with videos, much clearer explanations, and complete tutorials as we complete our own dam constructions as part of the 7 sustainable villages.
The first case study presented is Lawton’s permaculture property that he eventually sold to one of his students. The property is located North of Brisbane, Australia on the sunshine coast where it rains quite a bit. The property is 5 acres and zoned as a small farm, about half forested and half farm fields. The forested area was inaccessible because of a valley with a creek running through it. There are three creeks on the property:
Lawton completed the work successionally – taking approximately ½ of his time for 2 years. An image of the work (dams, swales, and roads) is shown in the screen capture below from the video where he discusses this case study:
The first thing Geoff did was install a dam to gain access to the forested side of the property that was originally deemed unusable – the road over the dam is what allowed access. A serious 8-meter wide spillway was also installed that fed back into the primary stream. It was big to minimize the erosion potential to the dam wall. During big rains, 1 meter of water would go over the spillway. A pump was installed with a float and weighted foot valve to transfer water to the top of the property. The inlet to the pump was held below the water surface with a weight and off the floor of the dam with a float. The next two were placed in succession on the secondary creek with the spillway of the upstream dam feeding into the dam in series and the second dam fed into the third stream that originated on the property. Lawton believes that replacing 20-year-old growth forest with bodies of water is beneficial because life is boosted by increased water retention.
When a wet spot was noticed at the top of the property, a contour dam (also called a top tank) was installed. It was supplied partially by the road and nature strip. Its spillway drained into multiple swales on-contour that were in-series to direct the water around the farm field. This contour dam had geese and ducks, which resulted in nutrient-rich water. When water is released during the dry season, it takes a couple of days to soak into the dry ground, then it only takes a few hours to soak the land with nutrient rich water.
Then in the bottom corner of the property, it started to get boggy after about 6 months. A neighbor began complaining about this effect, so Lawton dug a trench 2 meters wide, 1 meter deep and put the excavated material on the downhill side. When earth movers hit clay in the trench, they compacted it by hitting it with the back of the bucket. This half circle pond filled quickly. After this, a third large swale was added to further disperse the water throughout the property. Lawton hand-dug 8 to 10 meters every day for about a month and the swale ended up being more accurate than the excavator.
The neighbor continued to submit complaints and caught Lawton on a technicality, which led Lawton to improve upon his design even further. Lawton was not allowed to divert any flow from the secondary stream to the third stream. This led to the addition of another contour dam on the third creek that was connected to the dam on the secondary stream using a canal (angled banks going down to a flat bottom). Two spots were picked that were the same elevation to have easy control over the direction of the water flow. The lower dam wall was extended to cover both the secondary and third creek, which created yet another pond at the third stream. Mounds and swales were used to direct extra water into the third creek and with a slight height difference and sluice gate to direct water back to the secondary stream, so no water was being diverted from there.
Beyond this work, Lawton also had small swales near the simple temporary home near the gardened (bamboo and legumes) area for kitchen flows. These swales were 2 meters across, 1 meter deep and with 2 meters across and 1-meter high mounds. Graveled footpaths were also added between the gardens off the lower-corner dug pond, where water had been pooling near the neighbor’s property. Because the footpaths were next to the pond, they were partially flooded with water. He trellised over the pond and grew trees on the mound next to the pond and used water weeds as mulch for the garden. The last addition was a ridge point dam, which was the 7th body of water added to the property. Lawton essentially confused the catchment, melded them together and while he fixed one problem, he technically caused another problem, but creatively fixed that too. In the end, Lawton achieved the goal of having 15% of the property under water.
The second case study was a consulting project that Lawton worked on located in Clunes, Northern Wales. It was a hilly project serving as a demonstration and teaching site. The work completed included building two dams, a large lower valley dam and a small upper contour dam.
The entire process began with a plan on a good contour map. In the lower one, a mix of bad soil and clay were found, so earth workers and their machines had to find better material elsewhere on the property, as well as blend dirt together to attain the appropriate clay-content necessary for the keyway and water-side of the dam wall. This was especially important to do because the lower dam had a decent flow and catchment area to it. Valley dams, like this one, are important to seal.
The lower dam was built with a Jetty too. Jetties have to be pre-build before the dam is filled with water. These provide a clean edge to the dam and somewhere peaceful to sit. The top of the dam was also a minimum of 3.5 meters wide so tractors and other average-sized machines could go across it to trim growth or do other work. Topsoil was placed (it is like icing a cake) on the waterline and then hydro mulched with seed (i.e. sprayed with wet mulch containing seed). The hydro mulch contained pioneer trees, bushes, and cover crops, along with organic glue and shredded paper.
The lower large dam used a large spillway swale with level sills and was installed by ripping the soil with a tilted blade on contour. All heights were checked with a laser level (laser level emitter on tripod and laser receiver – earth movers sometimes have these for rent) and considered adequate when within 10 mm. The elevations were marked before starting and double checked along the way and at completion. To achieve clear water (the clarity of a dam at best is usually weak tea type of clarity), he installed three silt trap ponds before the dam and made sure the edges were well vegetated.
This second dam was installed 20 meters above the house and acted as their water tank. A dam holding about 125,000 gallons is less than half the price of a tank holding that same volume. It is more economical to build a key point dam on top of the property.
Notable comment from this case study: It can be surprising what you find when you start digging. You never quite know what you are going to hit. If you hit a big rock and you don’t know how big it is, have the bulldozer bump/ram (as hard as he can) the rock while you stand next to the rock. If the ground shakes, then it is a floater, meaning it has a bottom and you can typically move the rock out of the way or work around it. If there is no shake, the rock is part of mother earth. Earth moving contracts usually mention OTR, which stands for Other Than Rock, because rocks are hard to deal with and hard on the machines.
This page was created primarily from the information presented in Bill Mollison’s “Permaculture: A Designers’ Manual”, Geoff Lawton’s online Permaculture Design Course (PDC), and the talk by Zachary Weiss that was part of Paul Wheaton’s PDC. Here are some other resources we found helpful too:
Creating a water retention landscape is essential to securing a sustainable way of life. Life is centered around water and the strategic installation of earth dams and supporting water features provides water security. Creating a retention landscape with earthen dams serves several life-giving purposes, such as watering holes for wildlife, fire suppression, eco-system creation and support, irrigation, livestock watering, and long-term water storage within the soil. A DIY earth dam construction site currently does not exist, so that is the aim of this site. As we build our own earth dams, we will continue adding information from those experiences so that others interested in installing earth dams have access to all the essential details necessary to do so correctly and affordably.
Q: Where have earthen dams been installed?
There is a mention of several earthen dam installation in Australia on Darren Doherty’s website, which includes Yeoman’s Nevallan, Yobarnie Farms, and Falloon’s Taranaki Farm. Andrew Millison of Oregon State University’s Ecampus mentions some implementations in the US, such as Seven Seeds Farm and Wolf Gulch Farm. Sepp Holzer also built earthen dams on his property in Tamera and Krameterhof and Geoff Lawton has built several earth dams on Zaytuna Farm.
Q: What is the best way to compact the soil?
By using a rolling compactor (or track roller). A vibrating sheet foot roller is ideal if there is any doubt about sealing a dam.
Q: How many dams should my property have?
Have as many small earth dams as are practicable scattered throughout the landscape, some up high to harness water energy potential and some down low to support livestock/irrigation.
Q: How can I be sure my soil is good enough?
A geotech engineer could be hired for $200-$2000 who could assess the soil for its clay content and give you an accurate assessment of the structural integrity of the soil that is to be used for the earth dam and pond bed. They also provide a spec sheet that can be helpful to mitigate any unpredictable legal issues.
Q: What is the most common problem with energy efficient gravity systems?
Air locks are a common problem. From Wikipedia: “An air lock (or vapor lock) is a restriction of, or complete stoppage of liquid flow caused by vapor trapped in a high point of a liquid-filled pipe system. The gas, being less dense than the liquid, rises to any high points. Flushing the system with high flow or pressures can help move the gas away from the highest point, or a tap (or automatic vent valve) can be installed to let the gas out.”
Q: What happens if the dam begins filling as it is being dug and built?
It sometimes happens that dams fill up with water naturally very quickly and that is usually fine. A dam filling slowly while you are building it is ok.
Q: What can I expect from earth workers during construction?
During construction they used a few heavy machines, such as an excavator to dig trenches and build the dams. Lawton just had to mark the area with pegs. He found that it was easier if the excavator has a 45 ram bucket (made for golf course landscaping), because it can do a lot more with less positioning. Operators are skillful people. From Lawton’s experience the process begins the same way every time – pace around first becoming familiar with how much the other knows. Use lots of pegs so they have the information they need to get the job done accurately. Let the operator know that he/she can take his time and can put shape and form for an artistic touch. They appreciate this, because most sites want them on and off quickly. A good bulldozer driver minimizes movements to those solely used for positioning. A measure of how good they are, is cubic feet of dirt moved per unit of time. To test their skill, get them to pile up soil and spread it evenly without pulling the soil backwards – this needs to be done with feel and without back-blading.
Q: What is a stew pond?
A stew pond is a pond in a cluster of three synergistic ponds. This is a concept that includes three dams – a large, medium, and small. The large and medium dam are alternated between cattle and baby fish – cattle are allowed to wallow in one of the dams for some time and then the cattle are removed and a crop is sown and young fish are introduced. While the other dam is used to grow forage for the cows. Once the forage for the cows have matured, the cows are brought back and the mature fish from the other dam are placed into the smallest of the three ponds, called the stew pond. Here the fish mature until they are ready for the kitchen.