Water can with little energy (I think) be pulled from the air (big one built in France but the figures allude me right now but a google search pulled up this "the aerial well will yield 7500 gallons of water per 900 square feet of condensation surface"), along with water recycling and efficient use such as pipes dripping water of roots I think relatively little energy would be required.
On 9/29/07, Robin van Spaandonk <[EMAIL PROTECTED]> wrote: > > In reply to Jed Rothwell's message of Fri, 28 Sep 2007 14:28:38 -0400: > Hi, > [snip] > >The Israelis have pioneered > >subsurface irrigation which reduces consumption by about 2/3rds. > > Subsurface irrigation means laying pipes etc. which can be expensive. > There is a > much cheaper method, which should be almost as effective, and may well > help > considerably, particularly in the developing world. > > It is night time irrigation through surface channels. Channels on the > surface > have been used to irrigate fields for millennia. If the water is applied > to the > channel system after the ground has cooled, say around midnight to 2 AM, > and all > of it soaks into the ground, then it will all be subsurface anyway, before > the > Sun rises the next day. The trick is to ensure that not too much is > applied. All > of it needs to soak in. If any is left on the surface, then it will be > subject > to evaporation during the day. > > Even so, the surface is going to remain moist, and this small amount will > be > lost to evaporation, which makes the method a little less efficient than > true > subsurface irrigation. > > Getting the applied amount right, will be a learning experience for > individual > farmers, but well worth the effort in the long run. > > Needless to say automatic dispensing systems can be developed, which even > though > expensive for a poor farmer, would still be a much smaller investment than > a > whole pipe network. Those too poor to afford even this, can always do it > manually. > > Of course covering the ground with "litter" also helps, as water falls > through > between the matter, but sunlight is prevented from reaching moist ground > underneath. > Regards, > > Robin van Spaandonk > > The shrub is a plant. > >
