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Drought: Introduction
Drought is a normal aspect of Kentucky's climate. Unlike other
natural hazards that are easily identified, a drought is a non-event
that evolves as a prolonged dry spell. It may be difficult to
determine when a drought begins or ends. A drought can be short,
lasting just a few months, or persist for years before climatic
conditions return to normal. Because the impacts of a drought
accumulate slowly at first, a drought may not even be recognized until
it has become well established.
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Photo Credit: Paul Conrad/
Park City Daily News. |
The many concepts of drought reflect its varied impacts on people and
the environment. A meteorological drought is defined in terms of the
cumulative deficit of precipitation relative to what is normal for a
region over an extended period of time. While the impacts of that
deficit may be extensive, it is the deficit, not the impacts, that
defines a meteorological drought. An agricultural drought, in
contrast, is identified when dry conditions, often in combination with
warm summer temperatures, lower soil moisture to the point that crop
yields are adversely affected. Agricultural drought relates not only
to the magnitude of the precipitation deficit, but also its timing. A
deficit of soil moisture during the period of germination or early
growth may be more important than a larger deficit that comes late in
the growing season. Further, below normal amounts of precipitation
may be adequate to support crop growth if precipitation occurs on a
periodic basis. Hydrological drought, meanwhile, occurs when a
prolonged dry spell substantially reduces stream flows, levels in
lakes and reservoirs, and groundwater levels (Wilhite and Glantz,
1985). In the Barren River Area, hydrological drought affects
municipalities that depend on surface and subsurface water supplies.
Monitoring drought conditions is difficult because agricultural and
hydrological droughts do not always occur together. Agricultural
drought precedes hydrological drought, and likewise, responds more
quickly to a return of normal precipitation conditions. A
hydrological drought can linger on long after the grass has turned
from brown to green, making it difficult to convince water users to
conserve available supplies.
Unfortunately, efforts to mitigate the impacts of drought tend to be
reactive, involving crisis management (Western Water Policy Review
Advisory Commission, 1997). A proactive approach to drought that
emphasizes risk management promises to be both more effective in
limiting the impacts of drought and more cost efficient to administer.
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