Infrastructure: Dams, Roads and Swales
In the past 2 years a lot of our focus was on getting the main infrastructural elements in place. We first had to clear the semi flat area of the land to be able to even see most of it. Once we had a better view, we started planning what had to become a complete interconnected system of ponds, dams, gullies, swales and dirt roads. In this post we show the work that has been done and the results, in another post we’ll go deeper into the Permaculture design.
For a first impression, the picture below shows the road runoff we receive from a moderately strong rain shower. On this picture you see the water enter our ‘mud-pond’ which was built to loose at least some of the sediment before the water flows into the first dam.
Right after this mud-pond the water flows into a small dam (left on the picture below) which then overflows into the big dam (right on the picture).
The mud-pond, small dam and the big dam are situated on the key point, where the steep mountain slope above changes into the semi flat area in the middle of the land. The catchment area is roughly 8 hectares. In case of maximum runoff during a 4 hour thunderstorm there will be quite an amount of water coming down. For that reason we built the overflow of the big dam with as main goal to delay this flow of water. It has two 4″ tubes which would be about enough to handle a normal strong rain event. Above that an 8″ tunnel for more extreme rain and on top a concrete overflow on the lowest part of the dam wall
At the other side of this overflow there is a 3 meter wide swale to calmly transport the water over a distance of about 40 meters. The water that does not sink in overflows into a valley. In the design we added a series of swales bringing that water further out to help hydrate a ridge. Those swales we hope to build later this year.
In April 2015 we had the backhoe in again to construct 2 more small dams in the middle of the property. This is a small valley dam which we plan to enlarge along the road somewhere in the future.
We also improved our access to the land by constructing a road going up…
… and one going slightly down to the newly built valley dam. This road also provides runoff water to that dam.
Adding these 2 roads was a major improvement that allows us to now quite easily access areas that were previously difficult to get to.
Turns out that a backhoe is also a great piece of exercising equipment! At least according to Cris.
Then on to swales. We dig them by hand, which is cheaper and also good exercise. Below a picture of the start of what became our longest swale so far: 75 meters near the bottom of our semi flat area. It is also the border between our zones 1&2 and zone 3.
Another swale, dug between the new road going up and the almost level road going to the new valley dam.
Mostly when we plant a new swale we shield it from the bright tropical sun until the little trees had some time to properly root. After six months we remove the shade.
Below another swale to enlarge the catchment of a small ridge dam.
The pictures below show the results!
The overflow of the small key point dam…
… allowing the water to come down to the big key point dam.
Our main aim with these earthworks is of course water retention. But our added goal is to severely slow the water flow going down to the valley in wet years. This works because every time the water overflows somewhere it first has to rise the water level of a new large surface before that element starts to overflow into the next one. We have now several times observed how the flow between the small key point dam and the big one can continue for 6 to 8 hours after the rain stops.
In a future post we will look at the complete design for the farm.
About Permaculture San Joaquin – Colombia
We’re a nonprofit organization aiming to promote Permaculture through both demonstration and education. Our name, Permaculture San Joaquin, was chosen to identify with the little town of San Joaquin, the administrative area in which our farm is located. San Joaquin belongs to the municipality La Mesa, in the province Cundinamarca, Colombia.
We’re mostly working in our small team of three, Rene (originally from The Netherlands, with a permanent residency in Colombia), Cris and Margoth (who are both Colombian).
The farm is 10 hectares (24 acres) in size. The terrain is mountainous, a semi flat to moderately steep area in the middle of the property, surrounded by a mountain ridge shaped as half a circle.
Our work is still concentrated on the initial stage to create the basic infrastructure on the land. Several dams were built, roads were improved and added. We have been digging a lot of swales and terraces by hand and a lot more will be added in the coming months. We describe the process on this blog – https://permaculturesj.wordpress.com/.