Global Water Use by Agriculture--Current and Future Issues
Nov 01, 2017
Water is an essential component for the lives and well-being of people around the world, both directly in terms of water consumption--survival experts believe most human beings cannot last more than three days without drinking water--and the role that water plays in producing crops and livestock that provide food for our daily diets.
The World Bank estimates that on average, 70 percent of the world’s fresh water is currently used by agriculture. This figure reflects the share of all fresh water that is actively utilized or permanently withdrawn from its source, such as a lake, river, or aquifer, that goes for agricultural purposes. In order to meet the demand for food needed by the more than 9 billion people who are projected to live on our planet by the year 2050, it will be necessary to increase global food production by at least 50 percent over that period. That additional production will also require additional water withdrawals by agriculture, estimated at another 15 percent in a World Bank analysis. Globally, withdrawal of water for use in agriculture increased 7.3 times between 1900 and 2010, a rate of increase that was 66 percent faster than global population growth over the same period.
In addition to future population pressures, agriculture will also have to deal with the impacts of climate change on water availability. The most comprehensive climate models project that almost everyone will see greater variability of precipitation, including both more extreme storms and resulting flooding, while other regions will face longer and more intense droughts. In one 2002 study reported on in Global Environmental Change, it was computed that U.S. corn production losses due to this factor, already significant under current climate, may double during the next thirty years, causing additional damages totaling an estimated $3 billion per year. That figure quantifies losses for just one (major) crop in one country.
These two phenomena will almost certainly induce more crop losses and more prevented planting around the world than the historical norm would suggest. In addition, in some years, climate change will reduce winter snowpack and make less water available for irrigation purposes. Part of the reason that the recent drought in California persisted for so long was the below-average snowfall during the winters of 2011 through 2015, which reduced surface water provided through spring melting of that snowpack and forced authorities to reduce water from that source that would otherwise have been made available to farmers for irrigation purposes.
According to a 2010 study in the journal Hydrology and Earth System Sciences, about 62 percent of the 300 million hectares around the world that are equipped for irrigation draw that water from surface water. Since the Second World War, a number of political and even military conflicts have occurred between countries over access to water from major rivers that cross national borders. These rivers include the Nile River, where upstream countries like Egypt and Sudan have sought to limit withdrawals or diversions from the river by downstream countries such as Ethiopia, Uganda, Tanzania, and Burundi. Other river systems that have seen similar struggles are the Euphrates and Jordan rivers in the Middle East, the Ganges and Indus rivers in the Indian subcontinent, the Parana and Cenepa rivers in South America, and the Han, Helmand, Amu Darya, and Syr Darya rivers, all in Asia. The Pacific Institute maintains a database of such conflicts on its website (http://www2.worldwater.org/chronology.html) dating back to 3000 BC, as well as dozens more representing smaller-scale conflicts between states or provinces and even individual communities or villages within countries over access to water. For example, two clans in Somalia fought a pitched battle over access to land and water in 2005, with 34 reported fatalities. As this resource becomes increasingly scarce in the future, such conflicts are likely to proliferate.
The other major source of water for irrigation is groundwater, particularly for places like China and India and in the Great Plains of the United States. In that region, farmers from eight states (Wyoming, South Dakota, Colorado, Nebraska, Kansas, New Mexico, Oklahoma and Texas) have drawn water from wells drilled into the Ogallala aquifer for centuries, although most intensely since the invention of the center-pivot irrigation mechanism in 1940 by a Colorado farmer named Frank Zybach. A 2013 study by researchers at Kansas State University estimates that the Ogallala aquifer could be 69 percent depleted by 2060 at current utilization rates.
Combined, China and India account for 42 percent of the world’s irrigated land. It is no coincidence that both countries benefited substantially from the new dwarf wheat varieties developed by Dr. Norman Borlaug in the 1960's that spurred the Green Revolution. Those varieties perform best when farmers also have access to nitrogen fertilizer and irrigation water, which both governments invested in heavily at the time.
On the other hand, only 5 percent of cultivated area in Africa is under irrigation, and many farmers there are already experiencing the types of climate shifts associated with climate change. For small-holder farmers in that region to become more productive and thus more important contributors to the global food supply by 2050, they will need access to improved infrastructure, inputs, and practices. These changes will need to include broader adoption of water-conserving practices like no-till cultivation and construction of local water infrastructure such as catchment facilities to capture runoff and preserve it for crop and livestock use later.