In this concept rainwater will be the main source for human drinking water. The rain and storm water will be captured in especially designated areas. After catchment the water will be guided and filtered. After a thorough analysis, it will be if necessary further treated. (Reverse-osmotic filtering)

According to the WHO, every person needs about 80 litres of water every day for drinking, cooking, personal hygiene and washing. If we estimate a maximum occupation of Sitio Joaninha with 900 habitants, the amount of 72m3 water per day will be needed.

Source: www.sigrh.sp.gov.br/sigrh/basecon/bancodedados/plu/plu.htm

In January approximately 0.0077m3 water is falling per day on 1m2. One would therefore need 9351m2 of collecting area to provide everybody with water, which would make an area of 10,39m2 per person. In August when the rainfall is very low and reaches only 0,0013m3, per m2 and day, the area needed is already 55384,6 m2, which would make an area of 61,5 m2 per Person.

The surface water will be collected within the so-called water catchment areas, with a total surface area of 96950 m2. It will then, either percolate, evaporate or run off. The probability of percolation is reduced by a very high k-value of 10-7 - 10-8. But percolation ditches and the layer of plants, which will have been formed after the re-forestation program is finished, help the water to enter the ground. These water catchment areas should see an intense re-plantation process with the native vegetation of the Atlantic rain forest. Thus, the chance of erosion and quick evaporation will be reduced immensely.

Nevertheless, a water loss of 50 % through evaporation in this climate has to be estimated. At the foot of each water catchment area is a natural spring, which already is a natural outlet for the percolated water of this area. The re-forestation and therefore the retention of the rainwater will lead to an increase of below surface water. The water outlet of these natural springs will therefore increase as well. The water from these wells has to be controlled for its quality. A rule of thumb says, that if the water stays for 50 days under the ground it became perfect drinking water. Water, which did not evaporate or percolate, will be guided through a small creek bed where it is intensely oxygenised and finally made to join the spring at the foot of the area. The pollutant load of surface water is due to the conservation measures within the water catchment areas very low. Nevertheless, further examinations have to be made, in order to determine pollutants already captured by the water while in the air.

It is strongly recommended to further investigate the subterranean water flow within the water catchment areas. The here proposed measures are based on assumptions made according to available geological and tectonical data. Nevertheless, the underground water flow might be different than assumed.

Once all the waters are collected, they will be filtered by sand filter and stored in below surface cisterns. From here, the water will either be pumped into the individual water tanks or distributed by water lorry.

The restricted water catchment areas have a surface of 56742 m2. In them, no housing, agriculture of any kind or other matter involving human activity should be allowed. They can serve as green classrooms, where children and adults have the chance to learn more about the interrelated life cycles of nature. They also can have determined paths, which should not be left while crossing the restricted areas. The restrictions have to be adopted, because of the short distances the water will procure until it shall be used for drinking purposes. The shorter the way, the less are the possibilities of self-cleaning processes through percolation, oxygenation, and other natural processes.

These restrictions will be less severe when we come to the extended water catchment areas. The extended water catchment areas have an additional surface area of 40213 m2. Their outline follows the high-points of the hills, which means, that all surface water on this areas will flow eventually into the restricted water catchment areas. This asks as a consequence for a special behaviour from the people who want to enjoy these areas. Although the areas are quite ideal for leisure activities they require certain "don´ts" No soapy waters should be spilled, no oils, no chemicals like bleaches etc, can be used and pick-nick waste has to be carried home.

To be able to even out peak water supply one considers 100 m3 of water demand, instead of the 72 m3 of the actual need. Storage and filter calculation work with 100 m3. The low-velocity sand filter, which will filter all collected water, has an infiltration capacity of 0,06 - 0,3 m3 per m2/h and cleans 99,9% of all pathogens and all floating matter from the water. The total area required for the two filters will be 24 m2, considering an infiltration capacity of 0,2 m3/h per m2 sand filter. Storage capacity is calculated along the line of water amount fluctuation, and results in a total storage volume of 30 m3 for both tanks.

Source: www.umwelting.ethz.ch/Bilder/SWW/SWW14.JPG