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Advanced Hydrologic Prediction Service
What is AHPS?

Advanced Hydrologic Prediction Service (AHPS) is a new and essential component of our Climate, Water, and Weather Services. AHPS is a web-based suite of accurate and information-rich forecast products. They display the magnitude and uncertainty of occurrence of floods or droughts, from hours to days and months, in advance. These graphical products are useful information and planning tools for many economic and emergency managers. These new products will enable government agencies, private institutions, and individuals to make more informed decisions about risk based policies and actions to mitigate the dangers posed by floods and droughts.


Weather influences our economic and social lives in many ways. Severe weather can have impact on revenues and profits of businesses, large and small. Weather can also disrupt and disorganize communities. As our nation's population grows and infrastructure costs increase, natural disasters can threaten social stability. Weather forecasting was initially developed in response to the need of societies to protect themselves from storms, severe heat and cold, floods, etc., and minimize consequent economic losses. It is estimated that inland flooding claims 133 lives and property losses from flooding exceed $4 billion in an average year in the U.S. The National Weather Service (NWS) is our nation's agency entrusted with the mission to protect life and property and to enhance the economy.

Brief Background

Impelled by experiences with major floods in 1993 in the Midwest, the Des Moines river basin was selected as a test site for AHPS product development. The successful demonstration of AHPS on the Des Moines river was favorably received by local water resource and emergency management agencies. The devastating floods in the upper Midwest and Plains states in 1997 provided an increased sense of urgency. The NWS began AHPS implementation at our offices in Wisconsin, Minnesota, Michigan, Iowa, Missouri and North Dakota. AHPS was quickly expanded to include tributaries within the Ohio River basin in parts of Kentucky, Ohio, and western Pennsylvania. Nationwide implementation is currently underway, and AHPS is available today at over 2,500 locations from coast to coast, including Alaska.

While floods are impossible to prevent completely and there is not way to guarantee protection of property, the NWS and other federal, state, and local agencies have proved the loss of life can be greatly reduced with better forecasting.

What is the Source of AHPS Real-time Observational Data

The majority of the observed water level data displayed on the AHPS web pages originates from the United States Geological Survey's (USGS) National Streamflow Information Program which maintains a national network of streamgages. In addition, real-time water level information is collected from other federal, state, and local streamgage networks.

How Does Real-time Observational Data Get to the AHPS Web Pages?

The data from water level gauges around the country is gathered by the Hydrometeorological Automated Data System (HADS), operated by the NWS Office of Hydrologic Development.

HADS is a data acquisition, data processing, and data distribution system. HADS acquires and processes raw hydrological and meteorological observational data from thousands of ground based Data Collection Platforms (DCPs) owned and operated by hundreds of federal, state, and local agencies around the United States. Following the processing of the raw data, HADS delivers the observational data to the Weather Forecast Offices (WFOs) and River Forecast Centers (RFCs) in the form of collective data products tailored for each office's use. The WFOs and RFCs subsequently use the data in their hydrologic models and to create the informational displays viewed on the AHPS web pages.

How are AHPS Products Developed?

Using sophisticated computer models and large amounts of data from a wide variety of sources such as super computers, automated gauges, geostationary (GOES) satellites, Doppler radars, weather observation stations, and the computer and communications system, called the Advanced Weather Interactive Processing System (AWIPS), the NWS provides hydrologic forecasts for almost 4,000 locations across the United States. These forecasts are developed by our River Forecast centers and distributed by our field offices for a wide range of customers.

What are the Components of AHPS?

The current group of AHPS products covers forecast periods ranging from hours to months. It also includes valuable information about the chances of flood or drought. This information is presented through user-friendly graphical products. The products are identified by the logo. The information, such as the flood forecast level to which a river will rise and when it is likely to reach its peak or crest, is shown through hydrographs. Other information includes:

  1. the chance or probability of a river exceeding minor, moderate, or major flooding,
  2. the chance of a river exceeding certain level, volume, and flow of water at specific points on the river during 90 day periods, and
  3. a map of areas surrounding the forecast point that provides information about major roads, railways, landmarks, etc. likely to be flooded, the levels of past floods, etc.

An additional feature of the AHPS Web site is a map of the river basin and various points along the river for which information is available. The data are not limited to information about floods, but can also provide information about potential droughts. This core suite may change over time reflecting the changing needs communicated by customers.

Who Can Use AHPS?

AHPS forecast products are a basis for operation and management of flood-control structures. Emergency management officials at local and state levels use these forecasts to fight floods, evacuate residents, and to take other measures to mitigate the impact of flooding. As the population grows, people increasingly choose to live near water, creating an increased need for the NWS to educate the public about flood hazards and to improve flood forecasts. These products can be used by a wide range of people, such as barge operators, power companies, recreational users, farmers, households, businesses, and environmentalists.

Be In Touch

We would appreciate your feedback on these new AHPS forecast products. Let us know if they were helpful to you. What can we do to make them more relevant to you?

Find Out More about AHPS

Additional information on the Advanced Hydrologic Prediction Service may be obtained on line at

US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
1325 East West Highway
Silver Spring, MD 20910
Page Author: NWS Internet Services Team
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