Extreme Hydrologic Event Monitoring

When planning for a flood, there are three key questions that must be answered:  What areas will be flooded? How deep will the floodwaters get? When will the flood arrive? A flood inundation map library is a set of maps that together show where flooding may occur – and how deep it may be - over a range of potential flooding scenarios in a stream or river.

The USGS Flood Inundation Mapping (FIM) Program helps communities protect lives and property by providing tools and information to help them understand their local flood risks and make cost-effective mitigation decisions.

High-water marks are like footprints left behind by a flood — they show how high the water reached during a flood event. High-water marks serve as valuable data points for both educational purposes and scientific research, helping us understand past and recent flood events. Collecting this information is an essential and time-sensitive task for understanding flood risk and improving public safety.

To manage our water resources effectively, we need to understand how much water is available and its usefulness. The USGS monitors the nation’s water resources through various national observing networks that use a range of technologies and methods to assess real-time water conditions and predict future changes in water availability for human and ecological uses.

The USGS Water Resources Mission Area is assessing how much water is available for human and ecological needs in the United States and identifying where and when the Nation may have challenges meeting its demand for water.

As of October 2024, the USGS Groundwater and Streamflow Information Program supports the collection and (or) delivery of both streamflow and water-level information at 8,705 sites and water-level information alone at 3,460 additional sites. The data are served online—most in near real-time—to meet many diverse needs including the protection of life, property, the environment, and our economy.

Centennial Streamgages are USGS streamgages that have been in operation for more than 100 years.

The Willamette River Basin reflects the conflicting water demands between humans and ecosystems—particularly salmon— and the challenge resource managers face throughout the Pacific Northwest.

The U.S. Geological Survey, in partnership with the University of Alabama, is constructing a new Hydrologic Instrumentation Facility, a science and engineering facility that will support our water observing networks and research.

Did you know that earthquakes can cause changes in groundwater levels? Very large earthquakes can even cause water-level fluctuations in some wells thousands of miles away, depending on the local geological conditions around the well.

The U.S. Geological Survey is integrating its water science programs to better address the Nation’s greatest water resource challenges. At the heart of this effort are plans to intensively study several Integrated Water Science (IWS) basins—medium-sized watersheds (10,000-20,000 square miles) and underlying aquifers—over the next decade. The IWS basins will represent a wide range of environmental...

The Next Generation Water Observing System (NGWOS) supports water availability assessments, management, and prediction by enhancing water observations in basins that represent major U.S. hydrologic regions. NGWOS provides high-resolution, real-time data on water quantity, quality, and use, as well as advance the development and application of new sensor technologies and remote sensing methods.