The U.S. Geological Survey (USGS) operates 13,880 publically accessible real-time water data stations (query on February 8, 2011). These include 9,260 sites with streamflow data, 370 sites with lake and reservoir levels, 2,920 sites with precipitation data, 1,320 sites with groundwater levels, and 1,580 sites with water-quality data. These stations are operated by the USGS and funded in partnership with over 850 other Federal, State, and local agencies. USGS water data are used daily by government agencies, industry, and the public to manage and utilize water resources of the United States for domestic and industrial water supply, irrigation, flood control, recreation, and education.

Even with this extensive network, floods and hurricanes frequently create conditions for which additional data-collection stations are needed to establish and maintain real-time situational awareness and to document events for post-storm analysis. In response, the USGS has developed new Rapidly Deployable streamGages (RDGs) to provide real-time data for floods and other emergencies. RDGs comprise non-contract, radar stage sensors and satellite radios and can be set up to continuously broadcast water-level data within an hour of arrival at the location of interest.

Documentation of coastal-storm surge requires a more extensive network of temporary water-level gages to document the timing, extent, and magnitude of hurricane storm along a coast and nearby inland waterways. These networks are deployed in the days and hours just prior to landfall and have included as many as 105 units spread over more than a 100 miles of coastline. Sensors can be programmed to record date and time, temperature, and barometric pressure or water level. Post-flood elevation surveys using global–positioning systems and differential levels are used to relate the sensors and accompanying high–water marks to a common and consistent datum. Since inception in 2005, the USGS has used the mobile networks to capture surge data associated with 5 hurricanes a locations from Texas to Maine. These data are posted on the Internet at http://water.usgs.gov/osw/programs/storm_surge.html.

While data from USGS networks has long been a foundational enterprise for water-resource and environmental and emergency managers, engineers, and scientists, it has only recently become an everyday tool for millions of citizens interested in the rivers and ground-water aquifers which course through or underlie the Nation's forests, farms and cities. USGS water data have been available to anyone for more than a decade from the National Water Information System using a web interface (http://waterdata.usgs.gov/) or data services (http://waterservices.usgs.gov/). Now, the ubiquitous availability of mobile phones has spawned new services that deliver water-related information directly to users in real time. The earliest and simplest systems send text or email messages to mobile phones. The USGS StreaMail service (http://water.usgs.gov/wateralert/streamail.html) is an example of a text/email service for obtaining current water data. Local systems such as in the Seattle region have provided text/email alerts of flooding conditions have also been developed (http://www.kingcounty.gov/environment/waterandland/flooding/warning-system/flood-alerts.aspx). In 2010, the USGS launched the national WaterAlert text/email application (http://water.usgs.gov/wateralert/) to alert subscribers when data exceed user-selected thresholds for any USGS real-time streamgage, raingage, water-quality or groundwater monitoring site. The system sends emails or text messages to subscribers whenever the threshold conditions are met, as often as every hour.

Of course, getting the data to a user is only half the battle; users also have to be able to understand and act on it. New digital geospatial flood-inundation maps can more effectively illustrate actual or forecasted flood-water extent and depth in the context of the community setting and the infrastructure where flood-threatened populations live. The USGS is actively involved in the development of flood inundation mapping across the Nation. Working with partners including the National Weather Service (NWS), U.S. Army Corps of Engineers (USACE), the Federal Emergency Management Agency (FEMA), state agencies, local agencies, and universities, the USGS is providing flood inundation mapping science resources to help build more resilient communities. A internet portal to USGS flood-inundation maps and mapping tools is available at http://water.usgs.gov/osw/flood_inundation/.