I pulled this out of a piece I wrote for the UK a few years ago, where I was trying to fight the stupidity of cutting down trees because it was claimed trees were shrinking soils under buildings.
The trees and the buildings were the victims of the long term drought they had.
I was credited with saving about 40,000 trees with this system and the deep watering that is done here, lasted longer than I thought it would with the new invention. In fact, the first tree lecture I ever gave was about why it happened.
I found wet, moist soil right next to dry, dessicated soil beneath the edge of the plastic dam. I pursued this remarkable boundry with backhoes down to the depth of 6 feet.
The original is at
http://users.rcn.com/bobw.enteract/article1.html Here an excerpt:
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In response to the crisis of a similar drought in Chicago a few years back, I wrestled with the seemingly overwhelming problem of providing water to hundred of thousands of public trees in our parks and parkways. The indictment of trees in the UK that they extract large quantities of water was exactly my dilemma here in trying to sustain trees at what seemed to me to be the levels of their own practical needs. When I read that trees could transpire hundreds of gallons a day, I was disturbed by the advice of many to just sprinkle a bit or set 5 gallon buckets with holes in the bottom alongside trees needing intervention. Those interventions may have made us feel we were doing something, but unless the trees were actually benefiting, our best efforts might be sincere, but if looked at honestly, were really hollow and self-serving.
To me, traditional irrigation techniques were clearly inadequate under these crisis conditions; they were wasteful in evaporative losses or sent water to gutters and drains by runoff on the slightest grade. One of my primary design goals was not to have to visit a tree twice; there were so many trees in stress that any second visit to an irrigated tree was to deny another tree its first visit.
Just as in the UK, we had watering bans for lawns and car washing in the Chicago area and its suburbs, So, an unavoidable task was to convince the governmental agencies involved that our irrigation of trees deserved an exemption from their restrictions. It wasn't enough to argue that trees were valuable assets that would take years to replace in size and grandeur. There was the additional burden of our present irrigation methods being so wasteful or unwieldy that they easily undermined any request for emergency recognition.
Since I had decided to pursue the common sense quantity of drought irrigation for a tree, it seemed that I should provide the shortfall in rain up until that point in time. If we were short 6 inches of rain, putting 6 inches of water into the root zone was my goal. That unprecedented amount would appear inherently wasteful by traditional thinking, so I had to prove my system to be precise and frugal in keeping the water only at the chosen tree. The system had to adequately irrigate a tree in its root area without the waste of evaporation or runoff--and it had to earn the support of the public to justify exemptions from the bans.
The system is a water-filled polyethylene tube, inexpensively available as a stock item, about 14 inches in diameter and 6 mils thick. The empty tube encircles the tree--my rule of thumb was the dripline--and is filled with water sealed by a knot in each end. The weight of the water forms a dam and the ends are overlapped so that water can be poured into the middle somewhat like a child's swimming pool with the bottom cut out. This allows percolation into the soil while the tubing dam holds that water in place. The seal of the tube at the bottom is remarkably leak-resistant as the water softening the ground beneath also allows the bag to press down more flexibly and better seal the area. (The name, tree sausage, was given by the staff and taken up by the public. In an attempt to make it all much more scholarly, I called it the Hydro Kielbasa Polyethelus, but the system stubbornly remained the tree sausage.)
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Please note there are no weep holes or perforations in the tubing because that concept takes me back to a silly bucket with holes in the bottom placed next to a tree which is simply too slow and timid for this crisis. When the water inside the tubing dam finally percolates into the soil, the end-knots are opened and the remaining water in the tube is drained into the same area. The tubing is rolled up, tucked under the arm and taken to the next tree. We did that on an assembly line basis and this was the first level of my irrigation concept.
The system did everything asked of it; it was precise, frugal, escaped workman's compensation headaches because we lifted only the empty tubes without the weight of the water, and it was imminently reusable. However, I still wasn't satisfied.
Every tree we weren't able to visit because of time constraints could be a tree lost or put in decline, so I put the tubing directly on a fire hydrant, walked it in a circle around a grove of trees, brought the open end back against the first length of the tube like closing the circle in a question mark, and turned on the hydrant. The water flowing in the tube weighed the same as the stationary water in the first method so it acted as a dam, but it also supplied the water for filling without any additional work. Because the inside of the tubing is so slick, the water pressure of the hydrant is reduced along the length of the run and comfortably handled by the tubing's thickness. This second dynamic system was easily set up and positioned by one person and moves water for flooding at a few hundred gallons a minute.
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With this rate of flow, areas were filled very quickly and since the ground often absorbed the water more slowly than the water input, the dammed area was easily filled to my target depth of 5 or 6 inches. When that was reached, the hydrant was shut off, the tubing maintained its shape and the water percolated into the earth at whatever rate it chose--usually not more than 15 minutes. The tubing was then detached from the hydrant and rolled up toward the ponded area allowing any remaining water to flow ahead and out the still open end that fed the site.
Continued in the next post---