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The Surprising Effect of Agriculture on Rising Sea Levels

Efforts to meet freshwater demand by harnessing "fossil" groundwater contributes more to rising sea levels than melting glaciers.
 
 
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Photo Credit: Used under creative commons license from waterdotorg

 
 
 
 

Deep tube-well irrigation can result in hand-dug wells (pictured above) going dry. This can affect access to drinking water, as hand-dug wells and hand pumps are often the primary source for drinking water in many communities.

Earlier this week, The Guardian  reported on a  study that looked at rising sea levels from a new angle. The study found that efforts to meet increasing freshwater demand by harnessing “fossil” groundwater [groundwater that cannot be replenished for millennia under current climate conditions] contributes more to rising sea levels than melting glaciers. Since there it cannot be replenished, tapping groundwater results in land subsidence (downward-shifting of ground surface) and a one-way transfer of water into the oceans. Researchers involved concluded that the deep tube-well drilling for water has contributed to sea level increases by an average of a millimeter every year since 1961. Neither the climate community nor the water community had paid attention to this aspect of tube-well drilling before.

In 2009, an  IATP report referred to several other problems of deep tube-well drilling—a technology adapted from the oil industry—focusing on its role in industrial agricultural production. It pointed out that the tube-well “enabled industrial agriculture to expand to areas where such massive water transfers for irrigation were not feasible. Unlike traditional wells, tube-wells give access to “fossil” water in large quantities by driving a tube into deep aquifers and using a pump to suck water up,” that is said to have resulted in an  environmental catastrophe in Asia. Withdrawals exceeding natural recharge rates of aquifers are leading to the lowering of water tables and land subsidence in many other parts of the world. For example, in the United States, where 45 percent of irrigation water comes from underground, in the High Plains aquifer (which includes the Ogallala aquifer), water levels have declined more than 100 feet in some areas.

Yet, faced with multiple environmental crises, many countries in Africa are looking at groundwater as the last resort to help deal with their food and water security challenges. Over the last decade, in several African countries the use of  treadle pumps (most commonly used by farmers on small plots of land) has been promoted as an affordable option for withdrawing water from shallow aquifers. So far, groundwater bore wells have been confined to a few areas  where commercial farming is its primary beneficiary. But it may no longer be confined to small pockets. A recent  study by British Geological Survey estimated the total groundwater storage in Africa to be 0.66 million km (0.36–1.75 million km).3 Even though they warn that all of this water is not available for abstraction, it seems to suggest that there is plenty of water to meet the “growth” needs of Africa. This study comes out at a time when many international agencies are calling for investment in groundwater development as a way for meet the Millennium Development Goals (MDGS).

However, the temptation to promote groundwater development needs to be tempered with caution, as we know from the Asian experience. Our report argued that the “the easy access to state-subsidized energy services and equipment” enabled the expansion of industrial farming to otherwise water-stressed areas of Asian countries such as China, India and Pakistan. As is well known, the World Bank and other multilateral agencies played a major role in the spread of this technology in South Asia. Initiatives such as GW-MATE, which look at  approaches to reconciling groundwater demand with resources, indicate that the World Bank and other similar organizations recognize the mistakes of the past. This new caution on groundwater development doesn’t appear to be matched by other new initiatives.

 
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