Precipitation deficits, soil moisture, streamflow, groundwater, snowpack, reservoirs, agriculture, water supply, ecosystems, wildfire risk, heat, monitoring, and resilience planning
Drought
Drought is a period of unusually dry conditions long enough to create water shortages or ecological stress. It can affect soil moisture, crops, rivers, reservoirs, aquifers, ecosystems, energy, public health, and food systems, and it often develops slowly before impacts become obvious.
What drought is
Drought is not simply hot weather or a dry day. It is an abnormal shortage of water that lasts long enough to cause problems. Because normal rainfall varies by climate and season, drought must be judged against local expectations. A dry month in a rainforest and a dry month in a desert mean different things.
Types of drought
Meteorological drought begins with less precipitation than normal. Agricultural drought appears when soil moisture cannot meet crop or plant needs. Hydrological drought affects streams, reservoirs, snowpack, lakes, or groundwater. Socioeconomic drought occurs when water shortages disrupt goods, services, health, energy, or livelihoods.
How drought develops
Drought can build from low rainfall or snowfall, high temperatures, dry winds, low humidity, early snowmelt, depleted soil moisture, or heavy water demand. Heat can intensify drought by increasing evaporation and plant water use. Some droughts develop over months or years, while flash droughts can intensify quickly.
Water systems under stress
Drought can lower streamflow, shrink reservoirs, reduce snowpack, dry soils, and lower groundwater levels. These systems respond at different speeds. Soil moisture may decline quickly, while aquifers and large reservoirs may reflect years of wet and dry conditions. Pumping groundwater during drought can delay or deepen hydrological impacts.
Farms, food, and ecosystems
Crops, rangelands, forests, wetlands, and rivers all respond to drought. Plants may grow less, yields can fall, livestock may need supplemental feed or water, and fish can face warmer, shallower, lower-oxygen water. Drought can also increase tree stress, pest vulnerability, wildfire risk, and habitat loss.
Cities and economies
Drought can lead to water restrictions, higher water costs, reduced hydropower, navigation limits, tourism losses, and conflicts among users. Cities may depend on reservoirs, imported water, groundwater, or rivers that are affected differently. Planning must consider essential public health needs, industry, ecosystems, and long-term water reliability.
Monitoring and response
Drought monitoring uses precipitation, temperature, soil moisture, streamflow, reservoir storage, groundwater levels, snowpack, vegetation stress, and local reports. Responses can include conservation, drought plans, irrigation changes, water transfers, emergency supply measures, crop insurance, fire preparedness, and ecosystem protection. Early warning helps communities act before impacts peak.
Why it matters
Drought matters because water connects nearly every part of society and nature. A shortage that begins in the atmosphere can move through soils, farms, aquifers, forests, rivers, power systems, and food prices. Preparing for drought means managing risk before crisis, not only reacting after wells, fields, or reservoirs run low.