Saturday, March 26, 2016

How Does Nature Harvest Dew?

Nature understands something that humans have only recently begun to grasp - that when there is no rain, there is still water available in the air - water in the form of dew or condensation.  There are several species of animal on three different continents that have learned to harvest this dew and live almost exclusively off of it.

Perhaps the most impressive dew drinker is Moloch horridus, or the Australian Thorny Devil.  This animal is lives in an environment (the Australian Outback) with very little rain.   However, in the desert, because of large swings in temperature between day and night, there is often some dew on the ground in the morning.  Most of this dew is immediately evaporated after sunrise.  However, the Thorny Devil is able to use the "horns" or spikes on its body to collect this dew instead of allowing it to gather on the ground.  The Thorny Devil then channels this moisture to its mouth with special channels evolved just for this purpose.


The Australian Thorny Devil - Photo by Bäras
This same method has evolved on the other side of the world by an unrelated lizard, the state reptile of Texas, the Texas Horned Lizard,  or Phyrnsoma cornutum. The Texas Horned Lizard doesn't rely on dew so much as it does on rain drops after they hit the ground and splinter into much smaller particles.  These particles are caught by the horns on this animal and channeled to its mouth as well, using one way capillary channels.

The African Pygmy Mouse, Mus minutoides also exploits the same effect by piling small stones outside its den at night.  These stones collect condensation (perhaps partly from the mouse's breath) which the mice then drink in the morning.

Our favorite dew harvester, however, is the Fogstand Beetle of the Namib Desert, Stenocara Gracilipes.  This beetle inhabits a desert with less than one inch of rain per year!  How does it survive in such an arid environment?   They will stand on little ridges of sand in the desert when the morning dew rolls in and angle their bodies to 45%.   These beetles have microscopic water loving (hydrophilic) spikes that collect dew, and water moving (hydrophobic) troughs that direct the collected water to their mouths.  These beetles can drink twelve percent of their body weight in water each day using this method!

The Namib Desert Dew Drinking Beetle - From NSF, public domain
Is there any way that humans could harvest this dew, not to drink, but to grow food and trees?  Yes, there is.  It is called the Groasis Waterboxx PlantCocoon®, or Waterboxx for short.

The Waterboxx has taken the best insights nature has to offer, including the water loving spikes and water moving troughs and angled top, to collect dew in dry areas.  This dew is then funnels into a reservoir where it is stored by later use by the plant growing inside the Waterboxx.  The dew is slowly released by wicks into the soil. Rare rainfall can completely replenish the 15 L (almost 4 gallon) reservoir of the Waterboxx.  In this way, we can start trees and grow garden plants without watering.

The Waterboxx with tomatoes - you see condensation on the rim of the Waterboxx (where there are no ridges) but none on the ridges as there are microscopic bumps or pyramids there that collect and then funnel water down to a reservoir.  
The Waterboxx may even be able to recycle some of the water transpired (or, simplistically, 'sweated') out by the plant at night.  We haven't yet proven this, but plants release a great deal of water through special pores mostly on the underside of lids (called stomata) at night, and on still nights, it is likely at least some of this water settles on the lid of the Waterboxx and is collected.  


A schematic cut away view of the Waterboxx - dew is collected on the tan lid, sent down the siphons (shown here in red), stored in the green reservoir, and slowly distributed to the roots of the growing plant via a wick.  Photo from Groasis.com

The Waterboxx has been used all across the world but its use is just catching on here in the United States.  People are finding that they can grow some vegetables with the Waterboxx without ever adding water, and start trees without any water after planting.  Even better. because the trees develop deeper roots with the Waterboxx, the tree is then far more likely to survive subsequent droughts, even when the Waterboxx is removed and reused.

If you would like like to know more about the Waterboxx or see results of using it, visit our main website, www.dewharvest.com.


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