Nearly every part of the U.S. experiences periods of reduced rainfall and drought. Droughts:
- Usually last for a season or longer
- Are a natural, reoccurring feature of climate
- Are affected by human factors
- Are one of the costliest weather-related events
What causes droughts?
A drought is a period of unusually constant dry weather that persists long enough to cause deficiencies in water supply (surface or underground). Droughts are slow-onset hazards, but, over time, they can severely affect crops, municipal water supplies, recreational resources and wildlife.
Droughts do not occur spontaneously. They evolve due to lower-than-normal precipitation levels. Urban droughts generally affect areas dependent on reservoirs for water. Droughts usually lead to restrictions on non-essential water use, such as lawn watering and car washing.
If drought conditions extend over several years, the direct and indirect economic impacts can be significant. High temperatures, high winds and low humidity can worsen drought conditions and also make areas more susceptible to wildfire. Human actions and demands for water resources can also accelerate drought-related impacts.
Planning in advance for a drought can protect us in dry years. Here are tips on how to prepare for a drought both indoors and outdoors.
Indoor Water Conservation Tips Before a Drought:
- Never pour water down the drain when there may be another use for it. For example, use it to water your indoor plants or garden.
- Fix dripping faucets by replacing washers. One drop per second wastes 2,700 gallons of water a year.
- Check all plumbing for leaks and have any leaks repaired by a plumber.
- Retrofit all household faucets by installing aerators with flow restrictors.
- Install an instant hot water heater on your sink.
- Insulate your water pipes to reduce heat loss and prevent them from breaking.
- Install a water-softening system only when the minerals in the water would damage your pipes. Turn the softener off while on vacation.
- Choose appliances that are more energy and water efficient.
- Instead of using the garbage disposal, throw food in the garbage or start a compost pile to dispose it.
- Consider purchasing a low-volume toilet that uses less than half the water of older models.
- Replace your showerhead with an ultra-low-flow version.
Outdoor Water Conservation Tips Before a Drought:
- Check your well pump periodically. If the automatic pump turns on and off while water is not being used, you have a leak.
- Plant native and/or drought-tolerant grasses, ground covers, shrubs and trees. Once established, your plants won't need as much watering. Group plants together based on similar water needs.
- Don't buy water toys that require a constant stream of water.
- Don't install ornamental water features (such as fountains) unless they use re-circulated water.
- Consider rainwater harvesting where practical.
- Position sprinklers so water lands on the lawn and shrubs and not on paved areas.
- Check sprinkler systems and timing devices regularly to be sure they operate properly.
- Raise the lawn mower blade to at least three inches or to its highest level. A higher cut encourages grass roots to grow deeper and holds soil moisture.
- Plant drought-resistant lawn seed. Reduce or eliminate lawn areas that are not used frequently.
- Don't over-fertilize your lawn. Applying fertilizer increases the need for water. Apply fertilizers that contain slow-release, water-insoluble forms of nitrogen.
- Choose a water-efficient irrigation system such as drip irrigation for your trees, shrubs and flowers.
- Turn irrigation down in fall and off in winter. Water manually in winter, only if needed.
- Use mulch around trees and plants to retain moisture in the soil. Mulch also helps control weeds that compete with plants for water.
- Invest in a weather-based irrigation controller or a smart controller.
- Install a water-saving pool filter. Cover pools and spas to reduce water evaporation.
Always observe state and local restrictions on water use during a drought. Current drought information for Tennessee is updated here.
Terminology (from NOAA National Weather Service)
Meteorological Drought: Is based on the degree of dryness or rainfall deficit and the length of the dry period. Most droughts start with a meteorological drought.
Agricultural Drought: refers to the impacts on agriculture by factors such as rainfall deficits, soil water deficits, reduced ground water, or reservoir levels needed for irrigation.
Hydrological Drought: is based on the impact of rainfall deficits on the water supply such as stream flow, reservoir and lake levels, and ground water table decline.
During a Drought
Indoor Water Conservation Tips:
- Avoid flushing the toilet unnecessarily. Dispose of tissues, insects and other similar waste in the trash rather than the toilet.
- Take short showers instead of baths. Turn on the water only to get wet and lather and then again to rinse off.
- Avoid letting the water run while brushing your teeth, washing your face or shaving.
- Place a bucket in the shower to catch excess water for watering plants.
- Operate automatic dishwashers only when they are fully loaded. Use the "light wash" feature to use less water.
- Clean vegetables in a pan filled with water rather than running water from the tap.
- Store drinking water in the refrigerator.
- Avoid wasting water waiting for it to get hot. Capture it for other uses such as plant watering or heat it on the stove or in a microwave.
- Avoid using running water to thaw meat or other frozen foods. Defrost food overnight in the refrigerator or use the defrost setting on your microwave.
- Operate clothes washers only when they are fully loaded or set the water level for the size of your load.
Outdoor Water Conservation Tips:
- Use a commercial car wash that recycles water.
- If you wash your own car, use a shut-off nozzle that can be adjusted down to a fine spray.
- Avoid over watering your lawn and water only when needed. A heavy rain eliminates the need for watering for up to two weeks. Most of the year, lawns only need one inch of water per week.
- Check the soil moisture levels with a soil probe, spade or large screwdriver. You don't need to water if the soil is still moist. If your grass springs back when you step on it, it doesn't need water yet.
- If your lawn does require watering, do so early in the morning or later in the evening, when temperatures are cooler.
- Check your sprinkler system frequently and adjust sprinklers so only your lawn is watered and not the house, sidewalk, or street.
- Water in several short sessions rather than one long one, in order for your lawn to better absorb moisture and avoid runoff.
- Avoid leaving sprinklers or hoses unattended. A garden hose can pour out 600 gallons or more in only a few hours.
- In extreme drought, allow lawns to die in favor of preserving trees and large shrubs.
Using alert systems is crucial to being informed before and during droughts, just as with any other disaster. Our alert systems page has resources for a number of alert options.
Local Drought Risks
History of droughts in Williamson County
Overall, Williamson County has a low risk of being affected by droughts. However, our county is strongly agricultural and highly populated. If an incident of extreme drought were to occur, economic and life safety issues may occur.
While not occurring in Williamson County, extended periods of drought contributed to wildfires in East Tennessee on November 28, 2016, resulting in 14 fatalities and damage to more than 2,400 structures in Sevier County.
Although historical data in Williamson County is limited, drought is important to keep in mind since the rural nature of the county creates an economic dependence related to this hazard.
The National Oceanic Atmosphere Association provides a user-defined searchable online history of drought events in Williamson County. The figure below shows all events ranging from January 1, 2011 to December 31, 2020.
Ranking Local Vulnerability
Williamson County uses a simple system called a vulnerability calculator to determine each jurisdiction’s vulnerability to hazardous events, as shown in the charts below.