Letter Re: Air Wells, Fog Fences, and Dew Ponds–Harvesting Atmospheric Water

I am providing a link to a web page on “Air Wells”–the history of harvesting  atmospheric water, in the form of water vapor, dew ,and fog.  I know this was done in ancient times, and when I was in Europe I went on several tours of old castles, etc.  At one of these sites I saw a odd building on the grounds, and asked what that was used for.  It was used to collect water from the dew in the mornings, there was a cistern inside, and the water dripped from the tile walls and collected in the cistern.  The outside walls were some kind of ceramic blocks with holes through so the wet morning air could collect inside. 
I had read somewhere once that the indians in the desert areas had survived on dew collected in the night and early morning before the sun burned it off.  They did this by leaving a blanket out in the air or waving it around in the morning air and when it became wet they would wring it out into a container and do this until they collected enough water for the day.  This method was demonstrated by a couple of Boy Scouts at the national Jamboree sometime in the 1970s as best I can remember.  I read about it in one of the science magazines at the time, as I recall, it was Popular Science.  The article said that two Boy Scouts got up early in the morning and waved a blanket around in the air to collect water, then wring it out into a garbage can.  In about 20 minutes they were able to collect 20 gallons of water in the 20 gallon garbage can.   
Also I read an article years ago about a archeological dig in the desert in Asia or Africa where they couldn’t figure out how the city they found there survived in the desert with no apparent water source.  They found a clay tile pipeline that led to a hill.  There they found the remnants of an apparent dew collecting setup that supplied water to the city. 
Of course Rain water is the number one way to collect and harvest water, roof run off is good, but you must use a “roof washer” method to eliminate the bird droppings, etc as you don’t want them in your “cistern”.   I grew up on a farm in South Dakota, we did have a well which we used to water the livestock but it was very hard and a lot of iron and other minerals in it including iron bacteria.  We relied heavily on rain water for household use, since it is a soft water.  We had a gutter collection system that came off the roof to a ” Y” pipe with a switch over valve.  When it started raining we let the  rain wash the  roof clean (about 20 minutes of hard down pour) and then went out and switched the valve over to drain the roof water into the cistern.  This is a great method , but I have seen “automatic” switchover valves, where the runoff water flows into a bucket and then once heavy with water it closes the valve to dump the subsequent water into the cistern. 

CAUTION:   I would recommend you use a charcoal filter of the “Whole House”-type to filter the water going into the cistern, and another one on the water line being pumped from the cistern to the house plumbing.  There are always contaminants in the rain water that could be toxic these days.  From time to time we would find a mouse or rat floating in the cistern and have to fish it out and chlorinate the water.  This could be prevented by sealing the cistern off very well so this won’t happen. 
Also sailors at sea have often harvested water by rigging a sail or other canvas used for that purpose to collect rain water when raining and draining it into barrels or now days directly in the boat’s water tanks.  At suppliers that supply the boating community there is a device that you fasten into a canvas and it allows a common water hose to be screwed onto it and drain the water away to a tank. 

CAUTION: Don’t use a common green water hose for collecting water as they have been found to out-gas toxins into the water.   Use the white hose as sold by recreational vehicle suppliers for supplying water to campers, or use the black plumbing plastic pipe with garden hose style connectors.

I have an idea to put one of those fittings in the middle of a large tarp, connect it to a pipe, and roll the tarp up like a window shade and unroll it when it starts to rain that would minimize the collection of bird droppings on the water collection surface.  Then roll it up again after the rain stops.  If you put your water collection system on a hill above your dwelling , you can utilize gravity flow from the tank at the top of the hill.   Or you could put a tank on a stand above the dwelling and a roof or tarp above the tank to collect the water and also use the time-proven gravity flow supply method.  The beauty of these systems is that no power is needed to supply your water. (Except perhaps for pumping out the cistern, depending on how your house is sited in relation to your cistern.)   I hope this will be of use to someone.  – Darrell in Ohio