Beyond these traditional sources of water insecurity, climate
change is now affecting water supplies. Rising temperatures are
boosting evaporation rates, altering rainfall patterns, and melt-
ing the glaciers that feed rivers during the dry season. As the
glaciers melt, they are threatening to convert perennial rivers
such as the Ganges in India and the Yellow in China into sea-
sonal rivers, increasing both water and food insecurity. With the
earth’s climate system and its hydrological cycle so intertwined,
any changes in climate will alter the hydrological cycle.3
Among the more visible manifestations of water scarcity are
rivers running dry and lakes disappearing. A politics of water
scarcity is emerging between upstream and downstream
claimants both within and among countries. Water scarcity is
now crossing borders via the international grain trade. Coun-
tries that are pressing against the limits of their water supply
typically satisfy the growing need of cities and industry by
diverting irrigation water from agriculture and then importing
grain to offset the loss of productive capacity.
The link between water and food is strong. We each drink on
average nearly 4 liters of water per day in one form or another,
while the water required to produce our daily food totals at least
2,000 liters—500 times as much. This helps explain why 70 per-
cent of all water use is for irrigation. Another 20 percent is used
by industry, and 10 percent goes for residential purposes. With
the demand for water growing in all three categories, competi-
tion among sectors is intensifying, with agriculture almost
always losing. While most people recognize that the world is
facing a future of water shortages, not everyone has connected
the dots to see that this also means a future of food shortages.4
Water Tables Falling
Scores of countries are overpumping aquifers as they struggle to
satisfy their growing water needs. Most aquifers are replenish-
able, but not all are. When most of the aquifers in India and the
shallow aquifer under