Water is one of the main aspects to consider in an agro-ecological project and, of course, in a permaculture project. This is what will allow the magic called life. We are in a climate of great contrasts in precipitation level. It rains mainly in the fall and spring and rarely rains in the summer. There is also a great contrast between precipitation and evaporation, with an average annual precipitation of 600 to 800 mm in contrast to 1200 to 1300 mm of annual average evaporation according to the Spanish Meteorological Agency, which allows to guess the tendency for dry climate. Thus, in Terra Purna, the water is the central challenge in all phases, from catchment to distribution, through storage.
The strategy that we follow in this project is based on circulating the water to the greatest extent possible and infiltrating as much water as possible in the soil as this is the most beneficial and least expensive method of storing water. At storage level, in addition to infiltration, we also store water in tanks and ponds. In addition to the three streams and the rain, the catchment is made in a spring. In the future, the recovery of roofs rainwater and the use of condensation will also be considered.
The infiltration of water aims to raise the underground water more and more and thus the water of the subsoil will be more accessible to the life of the surface. For this we designed a swale running through the edible grove, i.e. a ditch on a level curve, about 3 meters wide and 1 meter deep. This swale passes in a keypoint of the terrain, i.e. at a confluence point of runoff water, but may also be fed by one of the streams that cross the farm. When it is full, the drainage is made by a set of channels that cause the water to circulate as long as possible on the terrain and then return to the stream. A second swale is expected to be built sooner below the previous. It will be interesting to see over time if the near-dry well of the neighbor fed by the vein of underground water that passes in that zone will have more water from year to year in the peak of the summer. We believe that yes and this will be a beautiful way to prove the benefit of these techniques.
In permaculture design we include several lakes, none of them waterproofed, a project we call water mirrors. Not having the fifth area sufficient for a larger lake, the design option was to make several small lakes some of them connected together thus increasing the water circulation dynamics. In this way, we obtain a total aquatic surface area closer to that of a larger lake. We think that one of the largest lakes to be located in a zone with deep sandy soil, if not waterproofed, will always lose water in the summer, which we resolve to accept. The other a little bigger, as there is a rock in the background, we hope that over time it will self-proof, leaving the challenge of diminishing evaporation with shadows so that it will never dry out, like perhaps trying to deepen it a little more, getting in the depths of 2.5 to 3 m, which will also reduce evaporation. The scheme of connected lakes is formed first by a small lake that absolves the infiltration of water in the upper part in the fifth transmitting that water directly to a larger lake which when filled passes the water through a small channel to a third shaped lake of dam. This third lake we call prey (from Spanish) has an overflow water flow through a 2 '' tube into a fourth lake. This fourth lake that is fed by a small stream that only runs when it rains in abundance is thus fed by the previous water retentions, maintaining for a longer time its level. It is worth mentioning that this fourth lake, which we call the lake of the orchard, allows a water infiltration under this vegetable garden, a solution that solves a flood that existed in this area when it rained heavily. the excess water of this last lake returns to the river completing the circuit.
For the drinking water circuit that starts at the source (water for direct consumption and for watering), the water is pumped into a tank in height only with a pressure pump SURflo from 80 watts to 24 volts forming a pressure group with a 24l pressure balloon (this balloon, identical to that of the expansion vessels of forced circulation AQS systems, is no more than a tank with an EPDM membrane inside). The pump power is designed to operate through a standalone photovoltaic system, working only in daylight when there is sunlight and while the storage is not full, which control is ensured by the pump's own pressostat and a simple buoy in the storage inlet . The use of the balloon allows the pump to be relieved of the small and sporadic consumption when the tank is full, since in this case there is always a reserve of 24 liters which are made available without activating the pump. The option of using a pressure pump with this power is due to the fact that it is a much cheaper solution (around € 120, pump + pressurized flask) and equally efficient, because it allows "change pressure by height", ie , every 10 m of height corresponds 1 kg of pressure, therefore making this pump approximately 2.4 kg of pressure, we lose pressure to the detriment of its elevation. In this case, the water that arrives at the entrance of the pump already with some speed is pumped to a deposit located to 10 meters of height with respect to the plane of the houses and the familiar vegetable garden, later allowing a gravítico distribution of the water. The strategy here is to put all the water at altitude to allow an asynchronous relationship between consumption and water abstraction, with the consequence of alleviating the spring operating pressure, thus giving more time for it to recover. As a deposit, we aim to build a deposit of about 10,000 liters in ferro-cement with an EPDM cylinder inside, guaranteeing the quality of the water and eventual leaks due to poor construction or degradation of the deposit. At the moment, we use two 240 liter barrels to close the circuit and establish the storage point provisionally.
All this intricate scheme of lakes that flow from one to another compensating, from infiltrations, the system of water channeled with abstraction, elevation, storage and distribution, already had enough "incarnations". In fact it has been a great laboratory in which we have learned a lot.