Given that 8 percent of food crops grows faster on farms using groundwater
than the aquifers are replenished, and many large rivers are so heavily diverted
that they do not reach the sea for much of the year, researchers believe
freshwater sources--underground aquifers and rivers--are stressed. Better
(5) management of soil and water and creative cropping patterns can boost
production from rainfall-watered cropland, but the heaviest burden will fall on
irrigated land. At present, most farmers irrigate their crops by channeling
water down their fields in parallel furrows.
One alternative, drip systems, enables farmers to deliver water directly to
(10) the plants' roots drop by drop, nearly eliminating waste by distributing water at
low pressure through a network of perforated plastic tubing installed on or
below the surface of the soil, where it then emerges through small holes at a
slow but steady pace. Because the plants enjoy an ideal moisture environment,
drip irrigation usually offers the added bonus of higher crop yields. Another
(15) alternative, sprinklers, can perform. almost as well as drip methods when
designed properly, but traditional high-pressure irrigation sprinklers spray
water high into the air to cover as large a land area as possible, and the more
time the water spends in the air, the more of it evaporates before use.
Despite the payoffs, the higher costs of these technologies relative to
(20) simple flooding methods have been a barrier to their spread, and so has the
prevalence of national water policies that discourage rather than foster efficient
water use. Many governments have set very low prices for publicly supplied
irrigation, leaving farmers with little motivation to invest in ways to conserve
water or to improve efficiency and most authorities have also failed to regulate
(25) groundwater pumping, even in regions where aquifers are over-tapped.
Therefore, farmers might be inclined to conserve their own water supplies if
they could profit from selling the surplus, but this practice is often discouraged.
Efforts aside from irrigation technologies are also conducive to the
reduction of agricultural demand for water; for instance, measurements of
(30) climate factors such as temperature and precipitation can be fed into a computer
that calculates how much water a typical plant is consuming, and farmers can
use this figure to determine, quite accurately, when and how much to irrigate
their particular crops throughout the growing season. But the most effective, if
unlikely way, to do more with less water is to reconfigure our diets, especially
(35) the typical North American diet, which, with its large share of animal products,
requires twice as much water as diets common in many Asian and some
European countries. Eating lower on the food chain could allow the same
volume of water to feed two Americans instead of one, and despite the resultant
loss of nutrition, this may be the only recourse for countries serious about
(40) reducing their aquifer strain.
The primary purpose of the passage is to

A. expose the fragile ecological conditions which modern irrigation technologies must ameliorate
B. argue that new irrigation technologies would ultimately be less efficient than a reconfiguration of the North American diet
C. argue that efficient water-use is dependent upon a mixture of various modern methods
D. provide an overall view of possible methods for lessening the strain on sources of freshwater
E. describe the cycle by which aquifers are depleted and then replenished through technology