“Green water”can go along way

Our bread,meat,milk and bananas,whatever we eat demands water–more or less depending on the type of food. Agriculture is the primary water user reaching up to 90 percent of water used in some regions.

With a rapidly growing population (already more than 7 billion people),water availability per capita reduces drastically. For instance,in India,water availability per inhabitant dropped from 5,177 m3 in 1951 (for 361 million inhabitants) to 1,820 m3 in 2001. It will drop further to 1,140 m3 in 2050 with a total estimated population of 1.64 billion.

There is a correlation between poverty,hunger,and water stress. The UN Millennium Project has identified the “hot spot”countries in the world with the highest number of malnourished people. These countries coincide closely with semi-arid and dry sub humid hydroclimates in the world,savannahs and steppe ecosystems,where rainfed agriculture is the dominating source of food,and where water constitutes a key limiting factor to crop growth.

The UN Food and Agriculture Organization (FAO) estimates that we need to increase the agricultural production by 70 percent to feed the 9 billion people by 2050. But,given the current global food crisis;boosting agricultural production will certainly increase the current water stress.

We need to urgently increase water productivity. How do we produce more cereals,milk,and bananas with less water? And what type of water are we talking about?

A matter of color

At the last World Water Forum in Istanbul three years ago,experts talked about the color of water:about 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.

However,the humble green water,is seen as ‘non-technological’,unreliable,and vulnerable to climate hazards.

Yet,agriculture depending on rainfall,this green water,represents 80 percent of cultivated lands (1.2 billion hectares) and 85 percent of agricultural water usage. Its importance varies between regions:over 95 percent in the Sahel;about 90 percent in Latin America;about 60 percent in South Asia;and 75 percent in North Africa.

For most of the global population and farmers,green water is more important than blue water.

Coping with unpredictable rain:the challenges of rain fed agriculture

In vast regions,especially in arid and semi-arid areas,rainfall is concentrated in a short rainy season (approximately 3 to 5 months),with a few intensive bursts,impossible to forecast and highly variable each year.

Farmers try and have to adapt to this hostile and unpredictable environment. They know the effects of water stress and the water retention capacity of different soil types. They have a very narrow crop portfolio adapted to their climate.

Any agricultural operation is about limiting the risks,so they are not encouraged to invest. Their time,the purchase of fertilizer or improved seeds,all can be destroyed if rainfall does not come in time.

Consequently,the crop yields in these farmers’fields are very low,lower by two to five folds than the researchers’or commercial farmers’fields. Change management in these farms is therefore a true challenge to harness the potential of rain-fed agriculture.

However,farmers in regions where rain is scarce or unpredictable or both,can use local solutions to make the most of the green water they get. Green water availability for farming does not only depend on the sky’s generosity. Farmers can improve green water efficiency before it runs off and when done successfully this can transform their communities.

Looking for solutions

Good water management in agriculture is not only about investing in high tech drip or pumping systems but also promoting local practices of rainwater harvesting,management,conservation,and efficient use in these under-developed agricultural areas.

The future could be in green water. How do we generate more green water and exploit the untapped potential of rain fed agriculture,largely neglected or misunderstood until now by agriculture policymakers and donors?

This is the topic of the session “A little rainfall can go a long way and feed many more:Act now”which will take place the 15th of March 2012 at the World Water Forum in Marseille,coordinated by the International Crops Research Institute for the Semi-Arid Tropics and the International Center for Agricultural Research in the Dry Areas,two international agricultural research centers of the CGIAR Consortium.

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