How to drain swamp and make a pond

thumbnailA friend of mine who owns a sizeable coffee plantation located at some of the highest areas of Central Panama asked me: “On my land I have several creeks and lots of water, I was wondering if we could make a lake there?” My usual reply to such questions is: “Let’s find out, when do we start?”

Turned out that he wasn’t joking about having lots of water. Down the bottom portion of one of his farms, there was a massive swamp, with several creeks flowing behind a green wall of mature secondary forest with lush undergrowth.  Before we could do anything, we needed some tough guys with machetes and chainsaws. We hacked at it for a week, for not only all the understory had to go, but I selectively cut many trees, leaving only the most valuable hardwood species and other useful trees. You can’t make an omelet without breaking some eggs, and we had fun doing so.

When the wall of green had been taken down, we found this:

before excavation

A fairly level, completely saturated valley, with two creeks and several sources. Since no machine could enter here, it was all down to manual labor to get this job done!

The first order of business was identifying the main source. Fortunately, the source releases surprising amounts of water and was therefore easy to find. Stones around the source indicated a primitive basin had been made here in the past to collect drinking water.

The spring starts where a graveled layer (tosca) meets the surface area. The gravel acts as as shower-head, making water pop up all over the terrain.  Therefore we excavated the main source to increase its volume and made a basin to catch and channel the water.

source

Now we could measure: an estimated 1100 liter per hour, 290 gallons, enough for several hundred people! Clean, tasty and perfectly safe to drink.

main drain layersNext step, a drainage channel for the main source and several smaller ones, cutting off the springs before they could feed into the swamp, draining them instead into the creek.

A large mudslide an estimated 40 years ago had buried organic material below a layer of loam and clay. Water filtered through this layer, tubing into the swamp. To prevent this, the channel had to be made fairly deep.

At last we could start on creating the objective: a fish pond.

starting excavation

 

constantino
A swamp fed by a source that releases millions of liters of water per year does not drain overnight. A second drainage channel was dug, also serving as the lowest point of the pond. Next, two feet of top soil rich in organic materials was removed and put aside.

The layer below was a perfect mixture of clay and gravel, before encountering more rocky layers. Excellent material to build a dam with, so we bagged the wet loam to be able to stack it.

 

 

A pond starts taking form. From here on it was all down to sheer muscle power:

Pond takes shape

The damn consists of a core of clay rich loam, covered by gravel, rock and loam to give it mass. Peanut grass (arachis glabrata) and vetiver are used to protect and stabilize soil. A week later and the pond is ready to fill:

before filling

Another week later:

end result.jpg

And that is how you drain a swamp.

Total project duration: 1 month with a crew of six.

Some afterthoughts: it’s amazing that in a steep and mountainous area such a fertile little valley has been overlooked for so long. Originating from a country that used to be nothing but swamp, to me it seems so natural to drain and use it. There is no avoiding my Dutch heritage: we love to manage water. As much as half a hectare of land was freed, which can now be used to grow plantains and coffee. The fish pond will be used to breed black pacu.

 

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