Adding multiple ponds to our permaculture style homestead is a major part of our mainframe design. We previously added swales and rainwater catchment because they were higher on the priority list. This spring we took the next step! We added two ponds (more will be added in the future). We are very excited to see how this pond develops over time.
Ponds bring huge value to a homestead. In permaculture, stacking functions is an important principle. It is not so much that permaculture adds functions to an element but that the individual practicing permaculture sees the multiple functions in the element itself. Many people might look at a pond simply as an aesthetically pleasing feature to a property. A good practitioner sees much more than that.
Here are some of the functions that ponds can provide to a homestead: water storage during emergencies; irrigation of nearby areas (we designed ours to flood irrigate our swales); Potential fire control; food production through plants, fish and waterfowl; micro-climate enhancement through attraction of beneficial insects, amphibians and birds; wildlife attraction; drought proofing the landscape; recreation; and yes, aesthetic pleasure, and much more.
"What will nature allow us to do here, what will nature help us to do?" - Wendell Berry
Ponds can be built anywhere but we would do well to heed Berry’s quote above. We look for areas where ponds want to exist. Low lying areas, wet areas, valleys (draws) where the least amount of dam wall can hold the most water etc… We can build dams on ridges, saddles, and flat areas but it will likely take more work. We want to achieve the greatest effect for the least input. We choose to build two valley dams: one small for many reasons but primarily to catch silt, flood irrigate swales and attract beneficial insects, amphibians, bees and birds. This one is above the “main” pond which will serve all of the functions listed above. On our main pond we carefully dug out, with an excavator, an initial trench in order to build the keyway (a highly compacted wall of dirt that stops the penetration of water). We packed the keyway as best as we could considering the circumstances and then dug out the pond area in order to obtain material for the dam wall. If a pond is not going to be lined (ours is not) with an artificial barrier it must contain sufficient clay content in order to seal and hold water. Our material content is questionable (one of our mistakes was to assume we have good clay content based on a small test pond) but I believe workable. However, the key to a good pond is the compaction of the material. Track rolling with an excavator works really well. Time will tell if this pond seals well. If not there are many techniques that can be used to seal ponds: adding clay material, adding bentonite, letting animals like pigs work the area for a time. If our pond does not seal we will use a combination of these techniques. For more detailed information listen to my podcast on building ponds.
Another very important aspect of pond building is to add a sufficient spillway based on a maximum rain event. Think of it as using calculations for a 100 year flood. This is a relatively simple process. Research your areas record 24 rain event, determine your catchment area and use an online calculator to determine how much water will flow through your pond in that period. Divide that number by 24 hours, again 60 for minutes and again by 60 seconds and that will give you the amount of water you have to contend with per second which is easier to think about in terms of spillway construction. Can that amount of water per second be handled by that spillway? Not sure? No worries, make it a little bigger.
The spillway needs to be at a height that corresponds to the amount of freeboard desired on the dam wall. Freeboard is the amount of dam wall showing from the water line to the top of the wall (same as a boat). For stability you want a decent amount of freeboard. Ours is designed at a little more than two feet. If my pond was really large I would have three to four feet of freeboard.
In the final analysis, our lessons learned are: first, we dug a diversion channel to divert seasonal water around the build site but made it insufficiently and therefore, we had a lot of seepage in the area which was challenging to work with. Second, we made a bad assumption with regards to clay content on the site. Portions of the site had excellent content (easily above 40%) and others were filled with rock and gravel. This caused us to pause (during an expensive excavator rental but we utilized it for other uses during that time) in our pond build in order to have material brought in. Finally, we dug the keyway area first and instead of completing that portion we excavated the pond area which became a bog and caused us to have to perform extra work. In hindsight, considering the inadequacy of our material, we would have completed the keyway first before excavating the rest of the site.
We learned an immense amount from the project and have no regrets. We cannot wait to watch this develop over the years! We cover more detailed aspects of homestead water in our homesteading workshops, check it out!
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