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Jul
14
2009
Capturing rainwater could give big boost to crops
When it comes to feeding the world, maybe farmers should think small. According to a study in the Journal of Hydrology, collecting rain in modest-sized reservoirs could provide enough water to substantially increase global crop yields.
The demand for agricultural water supply is growing, but large irrigation schemes can be expensive and environmentally unfriendly. The researchers modelled global cropland areas from 1998 to 2002 and found that the addition of small reservoirs such as tanks could have increased water flow to crops by 623 to 1,121 cubic kilometers per year. That in turn could boost cereal yields by 20 to 38 percent, they calculated, with most of the gains in Africa and Asia.
The authors caution that these results are only an initial estimate, and the development of small reservoirs will be complicated by issues such as local geology and land ownership. Capturing rain for crops could also decrease water flow to river basins, they note, potentially harming downstream ecosystems. – Roberta Kwok
Source: Wisser, D. et al. 2009. The significance of local water resources captured in small reservoirs for crop production – a global-scale analysis. Journal of Hydrology DOI: 10.1016/j.jhydrol.2009.07.032
Image © lenalir, iStockPhoto.com
Filed Under Fresh water, Socio-political issues |
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I remember going to my grandparents’ house 1959, when I was five, and again in 1963 and 1969. Their house, built in 1934, was on the side of a hill above the town of Trinite, in Martinique, and my grandparents had raised their seven children there with rainwater as their only source of water for drinking, washing, toilets, and every other use. The tank was at the back of the house, on higher ground than the faucets, but lower than the roof, so that the whole system required no energy input; it was gravity-fed. The only “energy” required was usually asked of family teenagers, especially visitors, about once every year during dry spells, to clean the tank. I remember it as a rather slimy job, which made me wonder at the time why we weren’t all sick from drinking this water. But no one ever was. In fact, I remember my mother savoring the water with delight. Built up immunity, it certainly was, because when my husband and I visited again for our honeymoon in 1976, he immediately had severe “Pelee’s revenge,” while I apparently still carried the right tools in my immune system.
Many people in Martinique had rainwater cisterns until the public utility company reached their homes. To this day, there seems to be a taboo about letting tree branches grow over one’s roof. I didn’t understand why people didn’t want to take advantage of the cool shade of trees, until I remembered the rain cistern and how fallen leaves sometimes had to be cleared from the screen that protected the gutter-to-cistern opening.
Today, as I drive through my present home city, Kinshasa, and its surroundings, witnessing the women and incredibly young children going on their daily chore of fetching water (in 20-liter containers - that’s 44 lbs!), sometimes miles away from their homes, and sometimes from even slimier and murkier places than my grandparents’ cistern, I wonder why this low-tech, relatively low-cost solution(compared to wells, pumps, reservoirs, and water distribution systems) is not used more widely in the developed world.
Any idea?
Hi Odile,
I’m not sure why rainfall collection isn’t more widely used in the developing world, but the authors suggest that, if small reservoirs were to be added to Europe and North America, the crop gains would be rather small. Instead, areas like East Asia and Western Africa with “pronounced seasonal distribution of rainfall of considerable rainfall depth” would benefit the most, they write.
Roberta