Too much bare ground is turning to desert. Allan has some surprising solutions - using herd of animals. Which reminds me to follow up on a solution presented to the Dutch public in 2010.
Disappointed that the Naga Foundation in Holland hasn't really got off the ground in doing proof of concept of the Peter Westerveld contour trenching project. Peter Westerveld had a good idea, but his talk at TEDx Amsterdam never really followed through. Naga started a campaign before doing the proof of concept in the region. They tell me that things are happening, but I don't see any recent reportages from the region.
Sander de Haas, a civil engineer in Amsterdam writes in a Linkedin discussion:
I’ve met Peter Westerveld in Kenya in 2005 and visited one of his contour trenching projects. Peter is a highly motivated person and has been constructing so called Sand Storage Dams for years. Sand storage dams are a proven technology that has been applied successfully in many countries. He has improved the water availability with these sand storage dams in many places.
The contour trenches are a ‘newer’ technique and are less well understood. We have had some discussions in the field with Peter because we were interested to understand the hydrological processes behind the contour trenches. If, and how, water is retained by these contour trenches is (in my opinion) not clear. If the groundwater level is deep (>5 m), which is the case in most of these dry places, the water will flow into these trenches and percolate downward (only vertically) towards the deep groundwater table. The water will therefore be lost for the local vegetation. It will add to the deeper groundwater, but that isn’t the purpose of the trenches.
I think these trenches can only work under certain specific local conditions. For example if there is a shallow layer with low permeability somewhere below the surface, so the water can’t percolate down vertically. Under these specific conditions a perched water table might occur, of which the local vegetation can benefit.
We have tried to discuss these issues with Peter and suggested to research the local soil conditions (augering) and install piezometers to measure the results of the contour trenches, but (sadly) Peter wasn’t interested in this research.
A few years later (I think around 2008) TU Delft started a research project together with Royal Haskoning and WCT (Peter Westerveld’s Foundation) on contour trenches in Vietnam. The only results I have seen from this project confirmed my ‘fears’ that the water only flows down vertically towards the deep groundwater and is ‘lost’ for the vegetation.
So to conclude, it would be a very promising technique, if it works. The pictures I have seen so far don’t convince me: everything in Africa turns green after a few rain showers. It would be interesting to compare two areas throughout the seasons: one with contour trenches, and one without. I’m not against any new techniques (on the contrary!), but it would be a pity if much labour and money will be spend on a technique that will only work under certain conditions.
Sieger Burger •
Update: after posting a question on LinkedIn, there was the following reaction:
Paul Martijn • Paul Martijn from the Naga Foundation reacted today (18th March)
Jonathan: Having watched the videos, the stories from Naga are still very fragmented. They don't explain the context, and we're not given much of a clue as what all this is going to cost. Why is this the best way forward and why not a hybrid solution. These nagging questions may explain the low scores of the videos on the YouTube channel (low 100's). Because the videos are not tagged, no-one knows they are there. Still a lot of work to do then, not just on the ground but online as well.