Preservation of Seasonal Rainfall
This blog post is my final blog post in the series of In-depth Rainwater Harvesting Methods. We are going to go Rock Crazy with Trincheras and Gabions. In the desert areas of Earth, these huge rock walls are used to preserve seasonal rainfall. In desert areas, a big percentage of the total yearly rainfall will fall in a very short period (hours). When large amounts of rain come to a torrential pour down, it causes extreme incidents of erosion.
Trincheras have been found centuries back in ancient Mexico. The design of the Trinchera is very important because they are free-flowing structures. In the design, you have to focus on the slope and contour of the land and stream bed. The most important part of the structure is a steady base. When designing your Trinchera, you also need to make sure that the lowest part of the land is in the middle of the structure.
A Gabion (from Italian gabbione meaning “big cage”; from Italian gabbia and Latin cavea meaning “cage”). The main difference between a Trinchera and a Gabion is that a Gabion isn’t free-flowing. The rocks in a Gabion are smaller rocks constructed in cages or wire baskets to build a wall.
Gabions don’t stop the water from passing through. They filter out debris, slowing down the water flow, allowing filtration, retaining the moisture into the soil, and reversing the evaporation. The most important thing to take away from the Gabion as a water harvesting method is that it will retain its loom. This is the key because of the loom contains the most fertile soil.
Step by Step How To Assemble A Gabion
- Purchase Gabion Bundles
- Open The Gabion bundles removing the folds
- Raise the side panels
- Fill the Gabions 1/3 of the way with stones
- Filling the Gabions, install the connecting wires *Important Note: Do not throw the stones into the Gabion from a great height*
- Overfill the Gabion by 2-5 cm
- Close and Secure the lid on the Gabion
- Add Layers by using cross ties at each end
- Place Geotextile between the backfill and the gabions
- Connect The Gabions
- You can fold the ends of the Gabions on an angle to adapt to walls
- Reducing length by overlapping Gabions and then Flipping them on their side
- Installation of a post in the last two gabions pre-installation
- Assembly for underwater placement
- Assembly for pipe going through the Gabion
Trincheras, Gabions, And Swales Together?
Have you thought about adding Swales with Gabions in the same rainwater harvesting design? In this video, Geoff Lawton (7 minutes in)combines on-contour swales and Gabions to create a better rainwater harvesting design.
Going through this series was so important for me, being able to share rainwater harvesting methods with everyone, so together we can help reverse desertification.
One of the reasons putting together and teaching at the World Permaculture Association’s Permaculture Design Course is so important is because with each person in every class there are two more hands in the soil dedicated to making a change!