State of the Planet

News from the Columbia Climate School

Agriculture: Big Water Use, Big Water Savings

india-feb-10-punjab-3921
Columbia Water Center: Punjab, India Feb. 2010

As in much of the world, farmers in Punjab, an agricultural state known as the “breadbasket of India,” grow rice via flood irrigation.  In this method, fields are flooded with several centimeters of water in order to kill weeds.  When the water dries, the field is flooded again – up to 40 times per season.  Clearly this uses a tremendous amount of water.  But just how much, and how does this compare to household use?

Each time a 1-hectare field is flooded (and most farms in Punjab are larger than 1 ha), approximately 500,000 liters of water are used.  A typical baseline figure given for water use for household consumption is 50 liters per person, per day (enough to meet basic needs of drinking, cooking, washing and sanitation).  Therefore 500,000 liters can provide water for 10,000 people for one day or for 27 people for one year.

In other words, if one farmer simply irrigates his field 39 times instead of 40, this can save enough water to meet the basic needs of 27 people for an entire year.  In Punjab, we are using a variety of tactics to reduce the number of times fields are irrigated. The goal of our work is to achieve thousands of fewer irrigations across hundreds of farms. If we are successful in doing so, the potential water savings, calculated in terms of household use, will be astronomical.

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Chuck Janisse
Chuck Janisse
14 years ago

I wonder how much water is lost through evaporation with irrigation systems involving open canals, and flooded fields? Whatever this loss may be, discovering and adopting alternative methods for agricultural irrigation that reduce or eliminate water loss through evaporation would certainly result in a more efficient use of available water supplies. Admittedly, there is a balance point between the economics of preventing evaporative loss, and the resulting water savings, but I wonder if this trade-off has been studied?