Much Irrigation Water Comes From Non-sustainable Sources - 12 February 2012.
Some of the water used worldwide for irrigation
comes from renewable sources such as local precipitation, rivers, lakes and
renewable groundwater. But some comes from non-renewable groundwater sources.
Because water supply for irrigation is so essential
to the world's food supply, it is important to quantify how much water comes
from sustainable sources.
Yoshida Wada conducted a global assessment of
how much water used for irrigation comes from non-sustainable groundwater
sources. They used a global hydrological model to simulate the amount of water
needed for optimal crop growth and the amount available from renewable sources.
They combined this information with country-level data on groundwater use to
estimate the amount of groundwater used for irrigation that comes from
nonrenewable sources.
Their results show that about 20 percent, or 234 cubic kilometers per year (56
cubic miles per year), of the water used for irrigation worldwide in 2000 came
from nonrenewable sources. The countries with the highest levels of
nonrenewable groundwater use are India, Pakistan, the United States, Iran,
China, Mexico and Saudi Arabia. Furthermore, worldwide, the use of groundwater
from non-renewable sources more than tripled from 1960 to 2000.
Source: www.eponline.com
February 12, 2012.