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| U.S. Geological Survey | Back | HydroHelp home |
| USGS Hydrologic Help |
USGS Hydrologic Help TopicsThe Water-Resources Discipline of the U.S. Geological Survey (USGS) operates in every State, with our mission being to provide water information that benefits the Nation's citizens. The links below allow you to further investigate water. |
General hydrologic concepts | |
| ♦ | What is a watershed? |
| We all live in a watershed. A watershed is an area of land that drains all the streams and rainfall to a common outlet. | |
| ♦ | Hydrologic unit codes and boundaries? |
| The watersheds in the United States have been delineated into hydrologic units. | |
| ♦ | USGS site numbers |
| USGS's water-monitoring sites are identified using a unique numbering system. | |
| ♦ | Typical USGS water-monitoring site |
| Look at some of the instrumentation that is installed at a typical water-monitoring site. | |
Surface-water concepts | |
| ♦ | Stream stage and streamflow |
| Find out how the height of a stream (stream stage) relates to the amount of water flowing. | |
| ♦ | How does the USGS collect streamflow data? |
| This website takes you through how USGS chooses a stream monitoring site, installs equipment, and monitors the stream. | |
| ♦ | How streamflow is measured |
| Find out the procedure that USGS scientists use to measure streamflow. | |
| ♦ | Determination of peak streamflows |
| Find out how USGS estimates streamflow during periods of extremely high water. | |
| ♦ | High-water marks and stream stage |
| "Low-tech" methods, such as a line of dried mud on a bridge pier, can tells us how high water got during a storm. | |
| ♦ | Streamflows during storms versus low-flow periods |
| Streamflow during storms can be many times higher than during low-flow periods. Find out how much of a yearly's streamflow can occur in just a few days. | |
| ♦ | Floods: Recurrence intervals and 100-year floods |
| Recurrence intervals define what a 100-year flood is. | |
| ♦ | Impervious surfaces and flooding |
| Find out why a house in Atlanta, Ga. is wearing stilts. Development in a watershed can alter streamflow patterns. | |
Water-use concepts | |
| ♦ | How much is a million gallons? |
| Water-use data are reported in million of gallons per day (Mgal/d). Find out how much this is. | |
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This URL: http://nts4dgaatl.er.usgs.gov:80/HydroHelp/index.cfm Last updated: 02/19/2004 01:56:54 PM USGS Privacy Statement || Disclaimer |