A drought refers to an extended period of deficient rainfall relative to the statistical mean for a region.

Drought can be defined according to meteorological, hydrological, socioeconomic, and agricultural criteria.

• Meteorological drought is qualified by any significant deficit of precipitation.
• Hydrological drought is manifest in noticeably reduced river and stream flow and critically low groundwater tables.
• Agricultural drought indicates an extended dry period that results in crop stress and harvest reduction. 
• Socioeconomic drought refers to the situation that occurs when water shortages begin to effect people and their lives. It associates economic good with the elements of meteorological, agricultural, and hydrological drought.  It is different than the other definitions in the fact that this drought is based on the process of supply and demand. Many economic goods (e.g., water, food grains, fish, hydroelectric power) have their supplies greatly dependent on the weather.  Due to natural variations in climate, some years have high supplies of water, but other years the supply is very low.

A socioeconomic drought takes place when the supply of an economic good cannot meet the demand for that product, and the cause of this shortfall is weather-related (water supply). Droughts in St. Louis County are of particular concern because of the potential for forest fires as well as the impacts lower lake levels have on recreation.

History

Droughts have impacted the St. Louis County area during different periods over the last century. The most notable drought periods were 1987-1989, 1976-1977, 1954-1961, and 1934. The two most recent winters, 2002 and 2003, had record low snowfalls. This has had an impact on the lake levels and increased fire danger. A socio-economic concern relating to a drought situation is that of water frontage property owners on the Thompson Power Hydro reservoirs.  Low water levels decrease the access some residents have to the reservoir.