I would like to pick your collective brain about the best approach to managing water on our property.
We are currently developing a 7,000 m2 plot of land in central Germany, south of Frankfurt, into a food forest. This region has a bit of a special climate in the context of Germany. We typically get 400-600mm of rain per year (decreasing due to climate change) and have more than 2000 hours of sunshine. Our record max temperature was set last year at 40°C+, our min low temperature in recent years was -12°C. Typical max temperatures in summer are around 30°C, typical low temps in winter around -8°C. 6-8 months of the year potential evaporation is greater than precipitation. In effect, this is a mediterranean climate and correspondingly, wine is the dominant agricultural product of the region.
Our plot is long (150+ meters) and somewhat narrow (40 meters). It starts in the West with a gentle slope downwards that bottoms out in a small depression about 70 meters off the eastern end. The remainder is basically flat and the plot is bordered in the East by a small stream. That stream is carrying water throughout the year, but carries the least amount of water of any stream in Germany when compared to its catchment area. The north side of the plot is on average a bit higher than the south side, although this also flattens out towards the stream.
We had very heavy rains this past week and on the lowest part of the plot a pool of stagnating water developed that took about a week (amid continuing intermittent light rain) to completely seep into the soil. Judging from rainfall records, we should expect similar rain patterns 2 to 4 times a year. On the other hand, no rain at all for several weeks, especially during the summer months, will be increasingly the norm, based on the experience of the past few years.
The plot was used for the past few decades as pasture for horses and hay field. It has been worked with heavy machinery, so there is probably some compaction. We still need to do a soil test, but from our digging so far we can say that the ground is somewhat loamy, more so in the lower lying parts.
Do you think that we need to invest in some form of active water management, e.g. swales, ponds, etc.?
We assume that we will have to water young trees for at least their first summer, if planted in autumn, if not for several summers. We are planning to have a well dug for that purpose. But in the mid to long-term, we would obviously like the trees, as well as other plant layers to be self-sufficient. We will obviously favor species and varieties that are as tolerant as possible to our specific conditions, although our winter low temps are just low enough to make some of the typical mediterranean species (citrus, etc) not viable.
We are currently considering to dig a few swales on contour to catch heavy rainfall runoff and facilitate seepage. At the plot’s low point, we are considering digging a shallow catchment to contain any overflow from the swales and drain the flatter part of the land (extending towards the stream) from stagnating water. I severely doubt that any permanent body of water would develop there, but it may turn out to be a bit swampy during parts of the year.
What do you think about our situation, considering that we want to develop a food forest that won’t rely on watering long-term? Do you think we should go forward with more active water management features like swales and catchment ponds, or do you think that the relatively high water table (as indicated by the existence of the permanent stream) will be enough to supply both trees and lower plant layers during times of insufficient precipitation, once our soil has been amended by increasing its organic content?
With 20inch of rain per year. I would say swales are needed. This will make the depression flood less, due to water sheeting down into it.
You are going to need more than just swales though.
1) Diakon Radish with 1m/3ft tubers and another 1m/3ft of fine hair root for 2m/6ft predill hole for your fruit tree roots, water and worms to follow
2) Nitrogen Fixers, with more dissolved minerals, your fruit trees need less actual water
3) Fungi 'root' are more efficient at getting water and minerals than plant roots, so let them trade.
4) Pest ridden, sick plants need more water to stay alive, so plant some herbs (onion+thyme+dill family, etc)
5) More Soil life, that is pooping, peeing and decaying means more bio-available nutrients aka manure factory
6) Carbon/Biochar/mulch/woodchip, will cut down on evaporation, help infiltration, reduce leaching of mineral, provide house and food for soil life.
7) Sea90/Rock dust/etc a bit of missing trace minerals
For me, I did 2 years of daikon radish + dutch clover + herbs, and then I mulched with woodchip.
My soil really needed the daikon radish for opening up the land quickly, and the dutch clover for pumping 220lbs of nitrogen/acre into the soil, and herbs for building up my population of good bugs. I thought about skipping this step and just adding mulch directly for a quicker fix, but I think this step was needed.
You might be able to put a fish pond in that depression.
It could even be chinampas style with a series of 5ft wide ditch/pond and 5ft wide berm/filled with vegetables/mushroom. I would get some ducks to seal it. And get water from the stream and or well to keep it full in addition to the run off upstream with a settling pond in between.
Iterations are fine, we don't have to be perfect
posted 9 months ago
thanks for your detailed reply. That is already a lot of valuable info. We had already planned on adding a mycorrhiza mix while planting and mulching with wood chips around trees. We were also looking to plant Elaeagnus and black locust as fast growing nitrogen fixers that would also provide fruit and firewood.
Animals are unfortunately currently not an option, though this may change down the road.
To start with, I think your situation looks promising if, as you say, your soil is predominantly loamy; if the soil had been too rich in clay, your trees would struggle to establish; if it had been too sandy, it would not hold water very well, which would exacerbate the effects of any prolonged period of drought. I've worked with both extremes - the more difficult one is the clay: when it's wet it's prone to compaction, and when it dries out it can become like concrete and crack really badly - not a nice place for tree roots.
Secondly, the gentle slope is also a good thing - a steeper slope would make rainwater run off too fast, and a very steep slope would make swales impractical and even dangerous.
The stream at the eastern border of your property can be a blessing, in that it opens some interesting landscaping possibilities. First (rather crazy) thing that comes to mind: I would try to build a small dam (if allowed by local regulations) and slightly modify the stream bed behind the dam, in order to create pooling of water (e.g., a mini-pond and/or wetland).
On the other hand, the stream can pose a threat if it overflows its banks during heavy downpours. More exactly, it can be a threat if you have any crops, earthworks, or structures in the floodable area - for example, if you had a fish pond in that area, it would be at risk in such a situation.
Swales are a good idea usually. They will definitely help you retain more water in the soil, as well as distribute water more evenly along the contour. However, they might NOT make a difference to the water logging at the bottom of your plot. Swales will slow water down and make it sink into the soil, but water will eventually end up in the lowest spot, no matter how it gets there.
If, as you say, your climate is mediterranean or quasi-mediterranean, I would definitely make sure to include fruit trees like apricots and jujube, which are quite frost-hardy, drought-tolerant (once established), and don't require much fertility.
I would think twice before introducing black locust. They can be very useful in places where nothing else grows - they are really tough SOBs - but if you can grow any other tree species, try to avoid black locust. I have planted quite a few on my property, and I'm grateful for their fast growth and the shade they supply in summer only a few years after planting (while many of my other trees are struggling!) - but I find that they impoverish the soil and are detrimental to other trees that are planted near them.
If you want to plant Eleagnus, I suggest you avoid Eleagnus angustifolia, whose fruit is not very palatable, and has very nasty thorns (similarly to black locust). Try E. umbellate, which has small but tasty fruit. Keep in mind though that it's an invasive species (just like black locust...).
So that's all from me. Best of luck with your project. Keep us posted!
I have the same type of climate and slope only north to south. Previous efforts to use tractors and cultivation of the flat part of the field lead to trying to make swales to drain standing water to avoid getting stuck. Not having animals or machines on the land now I observed there was a large Z pattern to the low spots therefore I have enhanced that shaping the ponds by hand and filling the ditches. Moles came along and enhanced the spreading and soaking in of the collected water. They dig towards the ponds as the field drys in our 3 to 4 month summer dry period. When the rains return the water fallows the tunnels back out int the dryer parts of the field. This year I am trying rice in the shallow ponds. If planted now there is enough time for it to ripen before the ponds dry out in June.
Skip to the last prt of this video to see what I am describing.