Friday, March 16, 2012

Rainwater harvesting is essential to feed the world

Jerome Bossuet in the povertymatters blog at the Guardian (UK): Whether it's bread, meat, milk or bananas, whatever we eat demands water. But with a rapidly growing population (already more than 7 billion people), water availability per capita reduces drastically.

...The Food and Agriculture Organisation (FAO) estimates that we need to increase agricultural production by 70% to feed the projected 9 billion people expected on the planet by 2050. But, given the current global food crisis, boosting agricultural production will certainly increase water stress.

We urgently need to increase water productivity. But how do we produce more cereals, milk and bananas with less water? And what type of water are we talking about? At the last world water forum in Istanbul, three years ago, experts talked about the colour of water: blue water (irrigation), green water (rainwater captured by the soil and available for plants) and grey water (polluted water that could be treated and recycled).

The hot topic was blue water, which is about technology – water that is pumped, stored, pipelined and distributed via a complex plumbing system. Blue water frees us from the increasingly unpredictable climate and has been hailed as a pillar of the green revolution.

Grey water results from our urban folly and frenetic industrial development but also, thanks to waste water treatment technologies, this is a "new" water source that could be reused.

Humble green water is seen as "non-technological", unreliable and vulnerable to climate hazards. Yet, agriculture depends on rainfall: on average it accounts for 85% of agricultural water usage. Its importance varies between regions: over 95% in Sahel, about 90% in Latin America, about 60% in south Asia, and 75% in north Africa....

A rainwater harvesting tank in Rajasthan, India, shot by Spiritualfade, public domain

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