Frequently Asked Questions

Water

The USGS monitors and studies a wide range of water resources and water conditions, including streamflow, groundwater, water quality, and water use and availability.

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Hattiesburg Flood Inundation Map
FEMA is the official public source for flood maps for insurance purposes: FEMA’s Flood Map Service Center FEMA’s Flood Hazard Map FAQs  NOAA is responsible for producing flood forecast maps that combine precipitation data with USGS streamflow data: National Flood Forecasts Interactive Flood Information Map Coastal Inundation Dashboard: Real-time...
Picture of tow truck driver assisting car stuck in flood waters.
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...
Flooded roadway
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...
Harmful Algal Bloom (HAB) in a stream
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...
Image: The Department of Agriculture (South Building)
When sulfurous, sulfuric, and nitric acids in polluted air and rain react with the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues, we see roughened surfaces, removal of material, and loss of carved details. Stone surface material may be lost all over or only in spots that are more reactive. You...
View of Cement Creek, Colorado
Mine drainage is formed when pyrite (an iron sulfide) is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Some or all of this iron can precipitate to form the red, orange, or yellow sediments in the bottom of streams containing mine drainage. The acid runoff further dissolves heavy metals such as copper, lead, and...
Image: Methane bubbles trapped in thermokarst lake ice
Methane (a gas composed of carbon and hydrogen) is produced two ways: Through biologic decomposition of organic matter at shallow depths. Swamps, landfills, and even shallow bedrock are some settings where this occurs.  Methane can also be derived over millions of years by high pressure and high temperature processes that produce fossil fuels deep...