FAQs

Plants naturally grow in and around lakes, but sometimes lakes and ponds can get an overgrowth of plants, algae, or bacteria. In many cases, humans are responsible. Chemicals that are used on lawns and in agriculture (like nitrogen and potassium) wash into our water systems. Once there, plants and algae have a feast on this “food”. Sometimes overgrowths of cyanobacteria (called “blooms”) can make...

Flood predictions require several types of data: The amount of rainfall occurring on a real-time basis. The rate of change in river stage on a real-time basis, which can help indicate the severity and immediacy of the threat. Knowledge about the type of storm producing the moisture, such as duration, intensity and areal extent, which can be valuable for determining possible severity of the...

There are two basic types of floods: flash floods and the more widespread river floods. Flash floods generally cause greater loss of life and river floods generally cause greater loss of property. A flash flood occurs when runoff from excessive rainfall causes a rapid rise in the water height (stage) of a stream or normally-dry channel. Flash floods are more common in areas with a dry climate and...

There isn’t a direct relationship between climate change and fire, but researchers have found strong correlations between warm summer temperatures and large fire years, so there is general consensus that fire occurrence will increase with climate change. Hot, dry conditions, however, do not automatically mean fire—something needs to create the spark and actually start the fire. In some parts of...

Wildland fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the aftermath of the fires. There is a need to develop tools and methods to identify and quantify the potential hazards posed by landslides produced from...

A drought is a period of drier-than-normal conditions that results in water-related problems. The amount of precipitation at a particular location varies from year to year, but over a period of years the average amount is fairly constant. In the deserts of the Southwest, the average precipitation is less than 3 inches per year. In contrast, the average precipitation in the Northwest is more than...

The beginning of a drought is difficult to determine. Several weeks, months, or even years might pass before people know that a drought is occurring. The end of a drought can occur as gradually as it began. The first evidence of drought is usually seen in records of rainfall. Within a short period of time, the amount of moisture in soils can begin to decrease. The effects of a drought on flow in...

To view the USGS streamflow information on drought, see the drought map on our WaterWatch site, which shows below-normal, 7-day average streamflow compared to historical streamflow for the United States. Links to additional maps and drought data are listed on the USGS Drought website and the National Integrated Drought Information System (NIDIS) .

Rainfall in any form will provide some drought relief. A good analogy might be how medicine and illness relate to each other. A single dose of medicine can alleviate symptoms of illness, but it usually takes a sustained program of medication to cure an illness. Likewise, a single rainstorm will not break the drought, but it might provide temporary relief. A light to moderate shower will probably...

An invasive species is an introduced, nonnative organism (disease, parasite, plant, or animal) that begins to spread or expand its range from the site of its original introduction and that has the potential to cause harm to the environment, the economy, or to human health. A few well-known examples include the unintentional introduction of the West Nile virus, chestnut blight, the South American...

Zebra mussels are an invasive, fingernail-sized mollusk that is native to fresh waters in Eurasia. Their name comes from the dark, zig-zagged stripes on each shell. Zebra mussels probably arrived in the Great Lakes in the 1980s via ballast water that was discharged by large ships from Europe. They have spread rapidly throughout the Great Lakes region and into the large rivers of the eastern...

The USGS documents the zebra mussel's geographic distribution and studies its behavior and biology. The resulting information is critical in helping to develop strategies aimed at containing and controlling the mussel's spread. Meanwhile, catching and transporting zebra mussels for use as bait, food, and aquarium pets is highly discouraged. We also encourage good boat hygiene: Wash your boat off...