Generally, a drought is a lack of water over a large area for a significant amount of time. It typically takes several months of below normal rainfall to move into long-term drought, and many months of above normal rainfall to recover from hydrologic drought. A drought can be divided into four different categories.

• Meteorological - occurs when there is a significant departure of precipitation below normal values.
• Agricultural - occurs when the soil moisture is not adequate for vegetation (crops) or livestock.
•  Hydrological - occurs when surface (lakes, rivers, reservoirs) and subsurface water (groundwater) levels are significantly below normal.
• Socioeconomic - occurs when the physical water shortage begins to have an effect on daily life

Drought conditions are assessed using precipitation amounts, stream flows, lake and reservoir levels, and soil moisture. In the 1960's, Wayne Palmer developed the Palmer Drought Severity Index (PDSI) based on temperature and rainfall. It is most effective over a period of several months, enabling it to measure meteorological and hydrological drought.

Palmer also developed the Crop Moisture Index (CMI) for use from week to week, instead of months. It is more efficient at measuring short term dryness or wetness, which will more easily influence agriculture.

In recent years, a new tool has been developed by the National Drought Mitigation Center, located at the University of Nebraska, Tracking drought blends science and art. No single definition of drought works for all circumstances, so people rely on drought indices to detect and measure droughts. But no single index works under all circumstances, either. That's why the Drought Monitor was developed, a synthesis of multiple indices, outlooks and news accounts, that represents a consensus of federal and academic scientists. The product will be refined over time as ways are found to make it better reflect the needs of decision-makers and others who use the information. Click here  to view the latest U.S. Drought Monitor.

 

Drought causes many problems. Loss of crops is one of the more costly effects of drought. Inadequate rainfall and the inability to irrigate crops directly affects the farmer and indirectly affects the consumer. Drought is also often accompanied by increased temperatures. Due to the lack of moisture, the sun's energy is used to heat the atmosphere instead of evaporating water. Wildfire is another series consequence of drought as a spark of lightning can easily trigger an uncontrollable forest fire. Severe droughts also have an impact on the daily routine for people as water conservation guidelines prevent water usage. One landscape-scale impact of drought is forced changes in natural plant community after drought-induced die out. Plant community impacts also accelerate erosion and diminish water quality and quantity. Rural and metropolitain communities document demographic shifts after periods of drought.

Drought Resources - Hay Hotlines (NDMC)  

National Drought Mitigation Center - University of Nebraska Lincoln

Managing Drought - North Carolina State University/North Carolina Cooperative Extension 

Drought Resources - University of Arizona

Colorado Drought Page - Colorado State University

Drought Resources - University of Georgia

Drought Resources - University Of Kentucky 

USGS Water Resources of the United States - USGS

NOAAWatch

The NOAAWatch Web site is a web site offering information about ongoing environmental events, and explains the role of NOAA in prediction, monitoring, and recovery from environmental hazards. It provides public access to current information on a number of environmental threats ranging from drought, to oil spills, to hurricanes and tsunamis, to space weather.

The page can be accessed by going here.

NWS/SPC's Severe Weather Information

Tom Priddy, EDEN POC for the University of Kentucky, has made available nationwide severe weather Web pages. By organizing information from the National Weather Service and the Storm Prediction Center, Priddy has made it possible for you to easily access real time severe weather information for your state.

The page can be accessed by going here.