North Dakota Water Science Center
Some areas of the United States are more likely to have droughts than other areas. In humid, or wet, regions, a drought of a few weeks is quickly reflected in a decrease in soil moisture and in declining flow in streams. People who use water from streams in these areas may face water shortages as soon as streamflow begins to decline. In arid, or dry, regions, people rely on ground water and water in reservoirs to supply their needs. They are protected from short-term droughts but may have severe problems during long dry periods because they may have no other water source if wells or reservoirs go dry.
Source: Moreland, Joe A., 1993, Drought: U.S. Geological Survey Open File Report 93-642, 2 p.