irrigation systems which drip water directly onto plants are one, precision sprinklers another.

It's urgent to implement new ways of irrigating crops. The maize farmers around me (SW France) are currently gearing up on new pivots and folding pivots in expectation of the GM bonanza that will see them throw more N and H2O inputs at their fields to get more yield. These irrigation systems waste energy pumping water high into the air and spraying it out as mist -- a great deal of which evaporates in hot weather.

What needs bringing online is a system of biodegradable microporous tube laid down by the seed drill with each row of maize (or some better system if that one doesn't look like a winner). Some judiciously-funneled CAP subsidies to compensate for their investment in the other crap, and firm direction from the technicians that it's time to change. There's no reason I can see why it couldn't be done.

When locusts move on, they leave nothing behind

There are real issues with irrigating marginal areas  leading to the salinification of arable land, a process that wouldn't occur if appropriate crops were grown.

But these are political problems and politicians are afraid of special interest groups such as the agro-chemical industry who will fund opposition to appropriate technologies that threaten their long (and short) term economic interests.

keep to the Fen Causeway

It's not all grim. There are some ways to begin to tackle the problem.

There is a product that takes almost any kind of waste water (including sea water and urine) and using cow dung (or "anything that burns") as an energy input and a process known as vapor compression distillation converts that waste water into up to 1,000 liters of clean drinking water per day.  (As a bonus, it continuously outputs a kilowatt of electricity.)

This apparatus is about the size of a washing machine and its target cost is $1000-2000 per unit.  It is hoped that communities such as villages in water-deprived areas can collectively finance the purchase and use of this product through microcredit ("We have 200,000 rural entrepreneurs who are selling telephone services in their communities... The vision is to replicate that with electricity"*).

• It is designed to supply a village with 1,000 liters/day of clean water. (Colbert Report)

• You can use any water source -- ocean, puddle, chemical waste site, hexavalent chrome, arsenic, poison, 50 gallon drum of urine. (Colbert Report)
• Vapor compression distillation is not new. Doing it in such an incredibly efficient way such that it takes only 2 percent of the power of convention distillers is new. (R&D World and Gizmodo commenter)
• The are no filters to replace, no charcoal, no anything disposable (just distillation). (Colbert Report)
• The Slingshot (as its called) can use half the waste heat (450 watts) from a sterling engine electrical generator (prototype also being designed by Kamen's company) to boil its water. (TED)
• The heat put into the water is recovered with a "counter-flow heat exchanger" and recycled to heat the next batch of water (that is part of the novel bit). (TED and Gizmodo commenter)
• Slingshot will be less then 60 lbs. (TED)
• The prototype slingshot was hand-built for $100K. The goal is to get production units down to $1,000 to $2,000. (CNN)
• The sterling engine, used as an electrical generator, can produce about 200 watts of power (it will never be more then 20 percent efficient) and 800 watts of waste heat (the waste heat that slingshot uses). TED
• Later sources say the sterling engine can generate 1 kilowatt or enough power for 70 high-efficiency light bulbs. (CNN)
• The sterling engine can run on anything that burns, propane or even cow dung. (CNN)
• The slingshot is a David and Goliath reference aimed at putting water and power back in the hands of the individuals. (AP)

Wired Science from Wired.com

I posted a video of the product in your Earth Day Water News Roundup.

Patent outline for "Locally Powered Water Distillation System" at the bottom of this page.

A language is a dialect with an army and navy.

This is typical for the American southwest, since you lose a lot of water to evaporation with the spray system. Regulations restrict the use of spray irrigation.