People associate global warming with temperature, but the phrase is mi

People associate global warming with temperature, but the phrase is misleading-it fails to mention the relevance of water. Nearly every significant indicator of hydrological activity-rainfall, snowmelt, glacial melt-is changing at an accelerating pace (one can arbitrarily pick any point of the hydrological cycle and notice a disruption). One analysis pegged the increase in precipitation at 2 percent over the century. In water terms this sounds auspicious, promising increased supply, but the changing timing and composition of the precipitation more than neutralizes the advantage. For one thing, it is likely that more of the precipitation will fall in intense episodes, with flooding a reasonable prospect. In addition, while rainfall will increase, snowfall will decrease. Such an outcome means that in watersheds that depend on snowmelt, like the Indus, Ganges, Colorado river basins, less water will be stored as snow, and more of it will flow in the winter, when it plays no agricultural role; conversely, less of it will flow in the summer, when it is most needed. One computer model showed that on the Animas River an increase in temperature of 3.6 degrees Fahrenheit would cause runoff to rise by 85 percent from January to March, but drop by 40 percent from July to September. The rise in temperature increases the probability and intensity of spring floods and threatens dam safety, which is predicated on lower runoff projections. Dams in arid areas also may face increased sedimentation, since a 10 percent annual increase in precipitation can double the volume of sediment washed into rivers.

The consequences multiply. Soil moisture will intensify at the highest northern latitudes, where precipitation will grow far more than evaporation and plant transpiration but where agriculture is nonexistent. At the same time, precipitation will drop over northern mid-latitude continents in summer months, when ample soil moisture is an agricultural necessity. Meanwhile the sea level will continue to rise as temperatures warm, accelerating saline contamination of freshwater aquifers and river deltas. The temperature will cause increased evaporation, which in turn will lead to a greater incidence of drought.

Perhaps most disturbing of all, the hydrologic cycle is becoming increasingly unpredictable. This means that the last century`s hydrological cycle-the set of assumptions about water on which modern irrigation is based-has become unreliable. Build a dam too large, and it may not generate its designed power; build it too small, and it may collapse or flood. Release too little dam runoff in the spring and risk flood, as the snowmelt cascades downstream with unexpected volume; release too much and the water will not be available for farmers when they need it. At a time when water scarcity calls out for intensified planning, planning itself may be stymied.

1/ According to the last paragraph, planning itself may be thwarted for which of the following reasons?

A Many regions lie in flooding areas and will not be able to be evacuated in time.

B The hydrological cycle for this century has become predictable, but experts are still uncertain about rainfall in certain parts of the world.

C There is too little information from last century to aid in the construction of dams.

D Information used to plan the size of certain environmental projects, such as dams, has become dated.

E Scientists are only just coming to appreciate the complexity of global warming.


2/ According to the passage, the likelihood that “dams in arid areas also may face increased sedimentation” will most likely result from

A an increase in precipitation

B a decrease in the annual snowmelt

C the rise in the average annual temperature of major rivers

D a shift in the seasonality of precipitation

E a rise in sea level


3/ The passage is primarily concerned with

A arguing how the world’s hydrological cycle is irrevocably changing
B highlighting the inadequacy of relying on last century’s hydrological cycle
C discussing the consequences of decreased water supply in dams
D warning against the unrestrained exploitation of natural resources
E describing how the Earth’s water will be affected by global warming


4/ Based on information in the second paragraph, which of the following can best be supported?

A Precipitation across different latitudes can differ significantly.
B An increase in soil moisture can have devastating effects on agriculture.
C Increased temperatures at sea level can affect the highest altitudes.
D Saline contamination mostly results from an increase in sea levels.
E Hydrological activity at one elevation has little to no effect on hydrological activity at another elevation.