Capturing Water With A Plastic Sheet

Ken — Sat, 05 May 2012 00:00:47 +0000

In a previous blog “Milking A Tree For Water” I wrote about the phenomena of transpiration and how to collect water by covering the end of a leafy branch with a plastic bag. This article explains a different approach using the same principal but by covering grass with a sheet of plastic.

I decided to simulate an emergency scenario by improving a condensation surface by cutting open a 16 gallon sized plastic bag to spread out as a sheet measuring 2.5 feet by 4 feet. Because of it’s thin material and flimsy nature, the slightest breeze could blow it away so I weighted it down with small stones at the four corners but it still fluttered with the breeze. That fluttering could spill any collected condensation back into the grass so I placed more stones around the edge until it was still.

I left this moisture collector alone for about a half hour then returned to find it holding a “beady” fog on the bottom surface. The first step in collecting this moisture was to protect it from touching the grass so I removed most of the stones including one at the corner. I pulled that corner of the sheet up and back until the entire sheet was completely inverted and laying flat on the grass. Then I gathered all corners together and lifted the sheet upward, thus consolidating the beads of water into larger drops that flowed down into the center of the sheet, forming a small puddle. I continued to tap the sides to consolidate all of the droplets into the bottom and then I carefully poured the puddle out the side and into a measuring cup (see picture insert).

Under the environmental conditions of the day combined with the size of the sheet I was able to collect about an ounce of water. Your results may vary. Larger sheets with greater surface area will yield larger volumes of water. It would be strategic to set out a number of sheets at the same time to increase the total yield of harvested water.

Subsequently I have used a thicker plastic sheet that I found much easier to control during the entire process. This would make a great weekend project that would familiarize you with the process and give you “hands-on” experience.

Transpiration -or- “Milking A Tree For Water”

Ken — Sat, 20 Aug 2011 11:07:56 +0000

I’ve enjoyed meeting new friends that I’ve met through the Contact page on this website. One of these friends whose name is Darrell related the following experience that he calls “milking a tree for water”. I wanted to share it with you. He writes the following: “…I was mowing the grass when a plastic bag blew across the yard, (it was a windy day). I grabbed it and looked at it, it was about the size of a garbage bag and clear in color. It looked like a new bag. I took it and pulled it over a branch of my lilac bushes to keep it from blowing away and continued mowing. A few hours later I looked at the bushes and saw it there, I had forgotten about it. I went to retrieve it and put it in the garbage can and noticed it was looking “all steamed up” and it had a cup of water in the bottom. Then I realized the bush was breathing water vapor and it condensed in the bag and the water ran to the low spot of the bag… (I) thought you may want to test and publish your results of this method of gathering or harvesting water from trees or bushes. I think people should be aware of this method of collecting water in emergency situations.”

As he suggested, I tried it for myself and made these observations:
– larger bags provide more surface area for moisture collection
– it’s a daytime process
– the amount of water produced is limited so consider setting up several bags
– avoid poking holes in the bag, especially on the bottom

Darrell discovered transpiration by accident, but I was pleased that he took time to share this phenomenon. This simple method can be an easily implemented and is another alternative in the quest for emergency drinking water.

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Capturing Water With A Plastic Sheet

Transpiration -or- “Milking A Tree For Water”