Waterharvesting Design

Small scale rain water harvesting and groundwater recharge through earthworks.

Our dream is to transform our homestead into an example of good rain water harvesting practices. Our plot is situated in a lightly sloping, rural landscape and has a size of 3000m2  We have about a thousand square meters (1000m2) of paved road sitting on the West and upslope of us, perhaps more if you count the house that evacuate their roof water onto the road. When it rains this road turns into a little stream. I have calculated that anywhere between 400 and 600.000 liters of water run past our land every year on an average rainfall. I hope to capture as much of  that water as possible and use it to bring our landscape into abundance, produce food and recharge the aquifer. Besides the benefit to our own lives and those of our children and grandchildren, we aim to to use this site as an example site for a variety of different earthworks that are useful in harvesting rainwater. In short, we aim for the mutually supportive functions of biodiversity, water abundance and spreading knowledge on water harvesting.

Collecting data.
The average rainfall for the area is somewhere between 400 and 600mm per year, the sources differ and seeing as Kato Souli is a town of only 1500 people I suspect there is no sound data because there is no weather station present. I would like to install a weather  station of our own for that reason. Like most Mediterranean climates this rain falls in late autumn and winter.
Besides rainfall data I also have gathered data on wind speeds, sunny days, average temperatures, evaporation rates, etc.

100 year rainfall event.
I don’t have an accurate measure for the area we live specifically, but using the most extreme ‘100 year rainfall’ of Penteli I find 100mm in an hour (these numbers were provided by Michaelis Diakakis, a researcher on flooding and other natural disasters in Greece).
Using that data I have calculated that in the 100 year event we can expect to see 150 to 200.000 liters of water run past in 24 hours. Therefore I hope to scale our earthworks to fit this amount of water. Anything beyond that would be returned to the streets.

Either way, even if we are just talking about the minimum of 400m3 in a whole year, that is a lot of water taken out of the race to the ocean and brought back into the soil for rehydrating the aquifer and future stream flows. Of course, it is a drop in the bucket if we look at all the water that falls, but this is what we can do within our sphere of influence.
To give a bit of a sense of the scale, this is what the street looks like in a ‘small’ storm. In this case about 60.000 liters passed by in 24 hours.

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The main goal would be to maximize the amount of storages for the water in the landscape.
In other words, to have a wide variety of ways for the water to be captured; like trees or other vegetation, animals, tanks, ponds and of course in the soil. Anything that would keep the water around and help create more organic matter in the soil. This would create a resilient network of elements with  beneficial relationships. Not only will this end up looking like a food producing water-park, but it will also perform as an education site for planting the rain.

Several different ways of harvesting, cleaning and storing water are being considered. In an ideal situation we would implement a version of all of these and more, but we are of course limited by time and money. We will most likely implement the major earthworks in one big go and then sequentially implement the other parts when time and energy permits. Here are some  of  the ideas.

– Road catchment drain and sediment trap.
– Gravel and reed pre-filter.
Swales for slowing, spreading and sinking the water. To be planted with fruit trees.
– Shallow well on the downhill of the swales. It would only be used minimally and to test how quick the water table recovers after installing the swales.
– Different ways of managing the overflow from the swales. Level sill spillway, sluice-gate, overflow pipes to direct the water, etc.
– Large roofwater storage for indoor use.
– Vertical helophyte filter, filtering black water. Overflows into the next item.
– Small scale artificial stream planted with habitat plants. Overflows into the wildlife pond.
– Wildlife pond. Functions to support as much biodiversity as possible. Clear clean water.
– Duck / fish pond / water storage dam. High nutrient load. To be used for fertigation.
– Possibly some small scale aquaponics.
– Water oriented playground. For kids to experiment with weirs, dams, sand and of course, water.
– Large infiltration basins around hardscape and important trees.
– Net and pan watering system around olive trees.
– Educate people through tours and signs the diversity of relationships between all of these systems.

Other important functions.

  • Water treatment
    We currently have one vothros (cesspit) that collects all of the waste water we produce. We also have the vactation house of the cousins to the North of us that could possibly be harvested. The vothros needs to go as it is polluting the water table. We want to design and use a system that recuperates as much household water as possible whilst composting the solid waste. Both grey water and treated black water will be used in the garden for ornamental plants and fruit trees.
  • Small scale alley cropping
    Utilizing windrows of trees on contour and a specific species selection, a system of alley cropping would be developed for rows of annual crops.
  • Home veggie garden
    A small scale area of about 200m2 for  home food production, utilizing a movable chicken tractor and localized mulch production.
  • Research into earth bermed buildings in the Greek climate.
    Earth is an excellent medium for regulating indoor temperatures. The average underground temperature at 80cm depth lies between 15 and 18 degrees. It would be very useful to research the use of modern day materials in building above-ground homes covered in earth. Above ground, because underground homes are almost always affected by soil moisture. Imagine a Greek version of a hobbit home ^_^
We are currently in the dreaming phase, which will be followed by the planning phase. After that we will move into the implementation phase. Of course we would end with some kind of celebration!

Call out!

In the first few months of 2020 I will be looking to team up with people to develop an implementation plan for this site and its features. I already had contact with David Spicer from Doc Spicer Permaculture Earthworks if he would be interested to do a course in Greece. He said he would be interested, but we have not gone into any details. The aim of this course would be to teach people about regenerative earthworks and water harvesting techniques. Also, we would be implementing the major parts of the design using excavators during or after the course. I would like to find networks and individuals to team up with for implementing this vision. I have included a contact form below to contact me if you would be interested.

A social aspect comes into this that I have not discussed yet. The land on which we live has been in the family for three generations and though people are interested in changing it, a period of time needs to be taken for adjustment to the ideas we are talking about here. This will be the most defining factor for when this course would take place. We are thinking in terms of a few years.