Friday, April 27, 2012
“Heart of Dryness”
Newly replaced rainwater pipe
I just read Heart of Dryness by James Workman about the plight of the Bushmen in the Kalahari desert when the Botswana government cut off their water supplies and how they adapted and how we can learn from them. I was interested in the book because I am originally from South Africa which abuts Botswana, and also here in Georgia we are engaged in legal water wars with neighboring states. Workman interlaces the story of the Bushmen with a narrative on the use and abuse of water worldwide and his view that water shortages will result in increased conflicts across the world as the world grows hotter. He does not believe dams are the solution in arid countries -dry heat and wind result in massive evaporation and build up of sediment reduces storage capacity. He suggests that artificial aquifer recharge where water is pumped and stored underground is more sensible, akin to the Bushmen burying their water in evaporation proof containers. Some of his findings are counter-intuitive, for example during holidays one Botswana school leaked nine times what it used while in session, due to pressure build up forcing water leaks through cracks. The 250 page book has 50 pages of notes/bibliography and appears well researched.
His reference to water wastage got me thinking of my own rainwater harvesting system and, since rain was in the forecast, I inspected and found several issues. Two gutter downpipes were blocked and no water would have been collected from them. Even more significant – the 4″ pipe which transfers water from my main collection point (the house roof) to my barn storage tanks, had again opened a leak where the 4″ corrugated pipe attaches to the 4″ pvc pipe.
The advantages of corrugated drainage pipe are that it is flexible so it will fit easily in a trench which isn’t straight or which has bends different from the available 90 deg, 45 deg or 22.5 deg fittings. And it is much cheaper, both the pipe itself and not needing expensive fittings for bends. Which is why I had used it for a section of the water run. Its disadvantages are that it does not make a tight fit when joined with pvc pipe and therefore can leak if there is a small shift in the moorings and, because it is corrugated, debris collects in it and causes blockages. Now I had to bite the bullet and replace the corrugated pipe with pvc pipe. I had used 4″ Sch 40 pvc pipe for the exposed overhead run – this is a thicker more expensive pipe. For the section I was replacing, which runs in a trench, I opted to save money (on the pipe and the fittings) and bought the considerably cheaper DWV pipe. DWV pipe (drain, waste and vent) is for non pressurized applications and because the pipe will be buried, fully supported by the ground and not sun exposed, this seemed a reasonable choice. It took some time digging a new trench (the old one was gradually curved and not usable) and aligning the pieces and fittings since the direction change was closer to 80 deg than an easier 90 deg. But now it is done and, with a dry season looming, I hope to be make every drop count.