A Quarterly Activity Bulletin of The South Carolina Department
of Natural Resources-Southeast Regional Climate Center
What is a drought?
Drought refers to a lack of precipitation over an extended time period. Droughts can be meteorological, agricultural, hydrological, or socioeconomical. Meteorological drought refers to dry conditions related to climate. Precipitation and/or evapotranspiration rates compare what is going on during the “drought” time with what is “normal” for the region. Agricultural drought refers to factors related to irrigation and soil moisture. These are interconnected with precipitation, evapotranspiration, groundwater tables, and reservoir levels. Hydrological drought refers to a lack in water supplies, often evaluated at the watershed scale. There is a lag time associated with hydrological drought, as lower water levels occur as a result of less precipitation and/or more demand on existing water supplies. Socioeconomic drought refers to the impacts on humans due to meteorological, agricultural, and hydrological droughts. It can affect the exchange of goods and services, and can reshape consumer habits and even cultural norms.
Examples of How Drought Affects Everyday Life
Fires are more common, soil erosion, soil quality reduced, dust/pollutants affect air quality, fewer trees (especially young ones) growing, damage to animal species as habitat changes, less food and drinking water for animals, migration and concentration (loss of wildlife in some areas and too many in others), fish habitats changed.
Land is less productive resulting in loss/damage of crops, insect infestation and plant disease changes as environment changes, wildlife in search of food damages crops, decreasing livestock birthrates/fertility/lifespan, milk/timber/food production decreases, fishing less productive, food price increase.
More irrigation necessary, new water infrastructure needs to be constructed (dams, pipelines), lower water levels in reservoirs and lakes and ponds, spring flow go downs, loss of wetlands, ground water depletion and land subsidence, water quality effects salt water intrusion, water temperature, pH, dissolved oxygen, turbidity), loss of aquatic organisms due to decreased flows.
Strain on financial institutions (foreclosures, higher credit risk), rural population loss and migration, loss to recreation and tourism industry, increased energy demand and reduced supply because of lack of hydrologic power, health-related low-flow problems (contamination, sewage flowing stagnantly, less dispersion of pollutants, fire-fighting capability lowered), loss of human life from heat stress, loss of aesthetic value of outdoors, public dissatisfaction with government drought response, higher cost for food and goods transportation.
Impacts from all four categories are interconnected. Without a doubt, any type of drought will somehow have an affect on our daily lives.
Indices such as the National Drought Monitor, the Palmer Drought Severity Index, and the Keetch Byram Drought Index help us to understand where droughts occur, when they occur, and how severe they are.
1. Drought Monitor
The Drought Monitor is based upon six national indices that measure national preliminary precip data, soil moisture models, daily streamflows, percent normal precipitation, topsoil moisture, and vegetation health via satellite. More information on these sources can be found at the following website: http://enso.unl.edu/monitor/archive/99/classify.htm.
Check out the National Drought Monitor website as well: http://enso.unl.edu/monitor/monitor.html
2. Palmer Drought Severity Index
This index is derived from preliminary precipitation data for the Southeastern states. Look at the color guage on the image to see how wet or dry the counties are.
To learn more about the Palmer Drought Severity Index, check out this website: http://www.dnr.state.sc.us/climate/sercc/products/drought.html
3. Keetch Byram Drought Index
A soil/duff drought index that ranges from 0 (no drought) to 800 (extreme drought) and is based on 8 inches of available moisture in the upper soil layers that can be used by vegatation for evapotranspiration. The index indicates deficit inches of available water in the soil. A KBDI reading of 450 means there is a deficit of 4.5 inches of ground water available to the vegatation. Factors in the index are maximum daily temperature, daily precipitation, antecedent precipitation, and annual precipitation.
How to Read the Keetch Byram Drought Index
To learn more about the Keetch-Byram Drought Index, check out this website: http://www.dnr.state.sc.us/climate/sercc/products/drought.html
Use the three different drought indices (Drought Monitor, Palmer Drought Severity Index, and Keetch-Byram Drought Index) to color each space. Match the index color with a crayon to color the picture. For instance, "D0" on the picture would be a "yellow" from the Drought Monitor, and you would color spaces marked "D0" yellow.
Permission is granted for the reproduction of materials contained in this bulletin.
Southeast Regional Climate Center
S.C. Department of Natural Resources
1201 Main Street, Suite 1100
Columbia, South Carolina 29201
The South Carolina Department of Natural Resources prohibits discrimination on the basis of race, color, sex, national origin, disability, religion, or age. Direct all inquiries to the Office of Human Resources, P.O. Box 167, Columbia, SC 29202.