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Dew ponds in Colorado?

 
pollinator
Posts: 1708
Location: Denver, CO
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I was wondering if dew ponds would work in Denver, Colorado. I don't desperately need a pond, I just thought it would be interesting. We have very hot, sunny days, cool nights, and dry air. If I laid out a sheet of plastic, ringed it with straw bales, lined the inside with loose straw, draped another sheet of plastic over the top of the whole thing, and put some rocks inside, could I have a dew pond? It would be a fun experiment, but I wouldn't like to try an experiment which is bound to fail.

I was thinking that if the experiment worked, a more elaborate pond of this type could be built for habitat, since using city water might be detrimental as well as expensive, and rain is too erratic.
 
Posts: 2679
Location: Phoenix, AZ (9b)
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Interesting - I have never heard of dew ponds before.

Like you said, you have dry air there. It might work in your cooler seasons - not sure about summer.

Also - other than as an interesting feature (which it certainly would be) - what is the goal of the pond? How does it stack functions with other parts of your plan? What functions would this element support and who are it's cohorts in supporting these functions?

One thing I've found it's easy to lose sight of, particularly on larger pieces of land, is the interrelatedness of permaculture design.

Something you might try to do to figure this out is to do an element analysis - like the now infamous "permaculture chicken" drawing.
--find out what a dew ponds needs are (certain humidity level, temp level, area/volume, way to keep the dew in one location, etc). Is there a naturally wetter area on the property that might slow down evaporation in your dry air? Like say where a downspout vents, or AC condensate drips?
--determine if you have a place where this would fit - like perhaps under some trees that would drip dew into the pond from their leaves AND protect the water from quickly evaporating later in the day...
--determine the energy needs in terms of the time, effort and materials to create it and the yield/payoff in the system.

Now granted I live in a harsher dryland than you do. And I've found that certain things are a waste of my time in Phoenix (raised beds, for example, except for wicking beds) but I have certainly tried my share of experiments and learned a startling amount from them. The ongoing result is that I have a much, much deeper appreciation for how a dryland functions and have been stacking elements and functions more in line with my climates needs and have stopped trying to create something that resembles gardens I've had in much wetter climates like Wisconsin or France. I would have never gained these insights if I didn't experiment. And I think understanding drylands is going to be one of the critical skills of the next 50 years as more and more land is desertified.

So I say try it if it piques your interest and keep good records on why you did what you did and what worked and what didn't and SHARE it so we can all learn from your experience. Please! =)

 
Posts: 9002
Location: Victoria British Columbia-Canada
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Studies have shown that dew ponds in Britain gather more water when surrounded by a larger bowl. They capture rain, fog and drizzle. I've never heard of one working in desert conditions.

The Atacama desert has whole plant communities that go on for decades without rain. Dew condenses on needles, stems and branches. Some drips or runs to the ground along trunks and some is absorbed through stomata.

Water has high thermal mass and doesn't make a great condensing surface. Try laying some sheet metal out with a slight slope, so that drips can be caught in a container. Metal cools quickly and will thus allow the process to happen. Measure what you get. If the result looks promising, consider a dew fence. If you get enough to fill a thimble, from a 10 sq ft area, there is hope.

If conditions are right, a dew fence will capture lots of water. If moisture is so low that the dew point isn't reached, you'll get nothing.

A simple indication of likely success would be dew on leaves at dawn. If they are wet, you are reaching the dew point. If they're dry, you are in the wrong place or trying it in the wrong season.

Have I mentioned that when the culvert under my road is in peak flow, it dumps about 53 acre feet of water per day into the valley ? I've had an unusual interest in watering deserts since I was a kid, but have always lived in moist environments.
 
Jennifer Wadsworth
Posts: 2679
Location: Phoenix, AZ (9b)
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Now I'm intrigued by all this. I, too, am fascinated (by necessity as well as by natural curiosity) of watering the desert. So many unique techniques have been tried.

Found this page on dew and fog harvesting: http://www.rexresearch.com/airwells/airwells.htm Lot's to digest there. Seems like metal or plastic, or things like palm fronds in my area, would make good condenser materials. In the hot desert, it looks like storage underground is the best solution as opposed to on the surface.

Great topic, Gilbert!
 
Dale Hodgins
Posts: 9002
Location: Victoria British Columbia-Canada
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The best condensing materials would be metals like aluminium and copper and galvanized steel. Scrap wire is a good choice. Fishing line has been used. When natural materials like palm fronds are used, a certain amount of water will be absorbed and lost later in the day through evaporation. This might work out fine in areas where there's lots of dew and fronds.

As water condenses, heat is given off. We want the water to run to storage immediately so that the collector can radiate gained heat to the night air. The cooler the surface, the more effective it will be in condensing moisture.

For systems that get cold enough to produce frost on the collection surface, it must be strong enough to bear the weight. Even in cold conditions, water is best stored in a container. Ice and snow can disappear through sublimation. They can evaporate without becoming liquid.
 
Dale Hodgins
Posts: 9002
Location: Victoria British Columbia-Canada
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Here's what wikipedia has to say about fog collection. One system was producing 15000 liters per day. http://en.wikipedia.org/wiki/Fog_collection

International Organization for Dew Utilization --- Everything we wanted to know is on their website --- http://www.opur.fr/
 
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