Questions: Water as a Resource

Question 1

What percentage of Earth's water is easily accessible freshwater in rivers, lakes, and shallow groundwater?

• A. About 50%
• B. About 10%
• C. About 2.5%
• D. Less than 1%

Answer: (D)

Less than 1% of all water on Earth is easily accessible freshwater. About 97.5% is saltwater. Of the 2.5% that is freshwater, most is frozen in ice caps and glaciers or locked deep underground. The rivers, lakes, and shallow aquifers that we depend on represent a tiny fraction of Earth's total water.

Question 2

Why can groundwater be considered nonrenewable in some areas even though water is part of the renewable water cycle?

Model answer: Some deep aquifers were filled over thousands to millions of years and receive very little recharge from current rainfall. When these aquifers are pumped faster than they are replenished, they are being depleted like a nonrenewable resource. The Ogallala Aquifer in the central United States, for example, is being drained much faster than it recharges, and some regions may exhaust their supply within decades.

This is a perfect example of how the renewable/nonrenewable distinction depends on timescale and usage rate. The water cycle is renewable, but specific groundwater reserves can behave as nonrenewable if extraction exceeds recharge. Once a deep aquifer is drained, it may take centuries or millennia to refill.

Question 3

Most of Earth's freshwater is in rivers and lakes.

• T. True
• F. False

Answer: False

Most of Earth's freshwater (about 68%) is locked in ice caps, glaciers, and permanent snow cover — primarily in Antarctica and Greenland. About 30% is groundwater. Rivers and lakes contain less than 1% of all freshwater. The sources we rely on most are actually a very small part of the freshwater picture.