|Water Resources of New Hampshire and Vermont
Providing Hydrologic Science and Data to Water-Resource
Managers and the General Public
Definitions of Drought
"Drought is a condition of moisture deficit sufficient to have
an adverse effect on vegetation, animals, and man over a sizeable
(Warwick, R.A., 1975, Drought hazard in the United States:
A research assessment: Boulder, Colorado, University of Colorado,
Institute of Behavioral Science, Monograph no. NSF/RA/E-75/004,
- "A period of abnormally dry weather sufficiently prolonged for
the lack of water to cause serious hydrologic imbalance in the
affected area." (Huschke, R.E., ed., 1959, Glossary of meteorology:
Boston, American Meteorological Society, 638 p.)
- "A climatic excursion involving a shortage of precipitation
sufficient to adversely affect crop production or range production."
(Rosenberg, N.J., ed., 1979, Drought in the Great Plains--Research
on impacts and strategies: Proceedings of the Workshop on Research
in Great Plains Drought Management Strategies, University of Nebraska,
Lincoln, March 26-28: Littleton, Colorado, Water Resources Publications,
- "A period of below average water content in streams, reservoirs,
ground-water aquifers, lakes and soils." (Yevjevich Vujica, Hall,
W.A., and Salas, J.D, eds., 1977, Drought research needs, in Proceedings
of the Conference on Drought Research Needs, December 12-15, 1977:
Colorado State University, Fort Collins, Colorado, 276 p.)
- Are We Having
a Drought Yet?
and Defining Drought
- Miscelleaneous Definitions
Because the definition of a drought can be a complex
issue, a collection of other definitions of drought follows.
Note that particular definitions may not be appropriate
for individual circumstances, and that some of the definitions
may be quite location specific. Other definitions can be
suggested for inclusion by sending email to the maintainer
listed at the bottom of this page; be sure to include a
full bibliographic reference for the definition.
- Drought: Dryness due to lack of rain... An absolute
drought is a period of at least 15 consecutive days to
none of which is credited 0.01 inches of rain or more.
A partial drought is a period of at least 29 consecutive
days, the mean daily rainfall of which does not exceed
0.01 inches. A dry spell is a period of at least 15 consecutive
days to none of which is credited 0.04 inches or more...
The definitions of absolute drought anf partial drought
were introduced in British Rainfall, p. 21, 1887, while
that of dry spell was first used in British Rainfall,
p. 15, 1919 [from Meteorological Glossary, Air Ministry,
3rd ed., London, 1944, p. 68.] [from Glossary of Geology
and Related Sciences, American Geological Institute, Washington,
D.C., 1957, p. 89.).