Back in October last year, I began an experiment in pond building. As I wrote then, it’s part of a strategy to retain water for longer in its passage through the quinta. Not just for irrigation purposes, but to increase the range of environments we have for growing and to support a greater diversity of wildlife.
But the ponds are rapidly becoming part of a developing long-term drought mitigation strategy as well. There are evidently years of severe drought here once every decade or so and at the moment it looks very much like that cycle is about to deliver another challenging year.
I’m already looking at this image and wondering how it was so easy to take this amount of water for granted. Well … it was easy because we’d never experienced what it was like not to have this easy constant flow of water through the land.
This is the second winter in succession the winter rains have failed. Last February, after one winter of no rain, the amount of water in the stream (left, below) was still pretty healthy even if half what it had been the year before. This February (right, below) we have barely a trickle.
The present low flow isn’t the full output of the spring our water comes from higher up the mountain – it’s as low as it is because most of the water is being used for irrigation already in the village above us. It’s brought into sharp focus the necessity for water storage here so we’re able to make much better use of what we get by filling storage areas during times of plenty and using the flow of the stream just to keep them topped up.
So my thinking is rapidly adjusting to the reality of drought conditions and there are plans to create rainwater harvesting systems as well as storing the stream’s output when there’s enough of it not to compromise supplies further downstream. If this summer is going to be a constant struggle to keep crops watered enough to grow, then I’ll cut right back on what I was intending to grow to a bare minimum and concentrate instead on building infrastructure so that the next time this happens we’re in a much better position to weather it. My aim would be to create enough storage to see us through a bad year. Whether we can do that perched on the side of a mountain with bedrock never far from the surface remains to be seen …
But back to the ponds …
There are already collecting tanks at the back of each terrace to hold water for the original flood irrigation system here. Over time, they fill with sludge from fine soil particles washed down in the water and decomposed falling leaves, etc. The top tank (the one in the picture above) was over knee-deep in sludge and beyond digging out by hand, so it’s been the plan for a while to bring in a small digger during the winter months to clear it out.
And at the same time this was done, I planned to have the digger create a new and much bigger pond (or ponds, depending on how the levels worked out) below the tank. The pond(s) would be created in the same way I made the ponds on the bottom terrace – by Sepp Holzer’s pig-style sealing methods – though this time with a more thorough sealing as we don’t have a pouço to keep supplied below.
If you’re not familiar with this method, Sepp Holzer discovered how to seal ponds naturally without the use of concrete or liners by watching pigs create a wallow. They stir up mud with their feet and trample the ground over and over until the finest particles settle out on top and form an effective, though permeable, seal that retains the water well. He has used this technique to make over 70 ponds and water-gardens on his farm, the Krameterhof, at altitudes ranging from 1,100 to 1,500 metres above sea level in the Austrian Alps, turning what was barren land and pine forest into one of the most productive organic permaculture farms in Europe. Though Holzer was doing this before Mollison and Holmgren even coined the term ‘permaculture’ …
He has also used the same principles in Portugal, in his work with Tamera in the Alentejo.
This is the pond area when we bought the quinta. The top irrigation tank is behind a mound of bramble-covered previous emptyings behind the golden-leaved chestnut tree at the back
Closer view of the same area after clearing, June 2010
And from further away, March 2011
The irrigation tank before emptying
Emptying begins
Sludge flow
Major sludge flow
Empty tank
Empty tank minus brambles, revealing post holes for a wooden trellis over this tank. Was it for growing vines over? Something to be reinstated perhaps …
Having emptied the tank, the work on digging the new ponds began. We had to go carefully. Irrigation channels that were built into this landscape when the terraces were constructed would be found somewhere in the area we were digging, carrying water from the top irrigation tank to the next level, but we had no idea of where they would be or how many.
The first irrigation channel discovered, part of large cap-stone removed
Close-up, showing the dry-stone schist walls and the fact the channel is built straight onto the bedrock
We were surprised to discover how deep the topsoil is
We found 3 channels in all, one from each side of the irrigation tank, and a secondary channel draining the levada at the back of the terrace. In places, these channels are not only laid onto the bedrock but actually cut into it – by hand – to ensure a steady gradient for the water so it would be unlikely to block.
The more I discover about the building and design of this landscape – design for entire river systems rather than individual properties – the more I become convinced not only that permaculture is only the first baby steps back in the direction of what mankind is capable of, working in tune with nature, but that our belief in our ‘progress’, ‘evolution’ and ‘development’ is pure delusion.
The way the levels worked, we ended up with 2 ponds. The next stage will be to dismantle and close the irrigation channel connecting the ponds (see below) to allow each pond to have a different water level. Once that’s done, then a pipe from the surface of the bottom pond will feed into the channel connecting to the waterfall on the next terrace down, so that when the second pond reaches its optimum depth, any excess will naturally drain to the next level.
Once that’s complete, I think we will be having a party and inviting lots of two-legged piggies to come and help us seal the ponds as they fill. That will be one for the summer months. But in view of the present drought conditions, maybe not this coming summer …
View across the two ponds showing the irrigation channel running between them
Sludge and ponds, the Wollemi pine to the left of the divide and the Giant Sequoia to the right
View from the top irrigation tank, showing the run of the irrigation channel
Once the sludge from the tank has dried out enough to be workable, it will be spread on the less fertile parts of the new fruit terrace and dug and shaped to link that terrace to the mound in front of the irrigation tank. And when we get some rain, it will be planted up with more shade-tolerant plants and things that grow well under walnut trees.
The stones forming the channels through the ponds will be used to build cascades from the tank to the first pond, and from the first to the second pond, edging to the ponds, and a small seating area above the first pond – I see no reason why designing a landscape for agriculture should be restricted to the merely utilitarian.