An interesting paper came out this week in the journal PNAS in which researchers say that the much-heralded drip-irrigation method of watering crops is often more wasteful of water than other methods, such as flooding. This is because crops watered in this way use all the water dripped at their roots, so very little seeps to the aquifers for other users. Such plants also grow faster and produce bigger yields – which consumes more water. And because drip-irrigation is subsidised, farmers extend their fields and so use more water. In total, the analysis shows a 15% increase in water use.
But is that fair? Flooding doesn’t return much of the water to aquifers, it is indiscriminate, often very badly managed, wastes a lot through evaporation, increases salination and leads to waterlogged soils. Drip irrigation makes sense because it is so precise, and better yields and faster growth is a good thing. Crops that have been genetically modified to grow faster and with bigger yields regardless of how much water they consume are another matter, of course, but in terms of more crop per drop, drip irrigation is surely the best option.
And it needn’t be expensive or use hi-tech equipment. Indian farmers have been using reels of ‘pepsees‘, a black-coloured version of the plastic tubing that popsicle ices come in, to drip feed their fields for next to nothing, as Fred Pearce describes in his excellent book on water management, When The Rivers Run Dry.
Agriculture is one of the biggest water users – and wasters. And one of the biggest problems is that the most thirsty types of crops are planted in innapropriately in the world’s dryest areas. It’s only going to get worse as the monsoons become more erratic with climate change.