USGS In Puerto Rico Provides Vital Stream Flow And Rainfall Information During Hurricane Georges

September 30, 1998

Hurricane Georges approached Puerto Rico on September 21, 1998 as a Category 3 hurricane. According to the National Weather Service, Hurricane Georges had sustained winds between 110 to 130 mph and gusts that probably exceeded 150 mph in the mountains of central Puerto Rico. The hurricane made landfall in Humacao and exited through Hormigueros, tearing a path along the central part of Puerto Rico*. Not since hurricanes San Felipe in 1928 and San Ciprian in 1932, had the island been bisected lengthwise by the path of a hurricane.

Hurricane Georges produced heavy rains over Puerto Rico, especially in the interior of the island. The U.S. Geological Survey raingage network* reported 24-hour rainfall totals that ranged from less than 5 inches in most of northern Puerto Rico to about 25 inches at Jayuya near the island's geographic center.

Hurricane Georges caused tremendous damage to the infrastructure of Puerto Rico. According to Government officials, 99.5 percent of the population was left without electricity, 77.2 percent without water, and 24 percent without telephone service. Many municipalities in the central part of Puerto Rico were isolated from the rest of the island because of bridges that were swept away and broken trees blocking the roads. Numerous landslides have been reported throughout the island.

The USGS continues to play an important role in providing scientific information before, during, and after the passage of hurricanes. The USGS maintains a network of 123 near real-time gaging stations in Puerto Rico for measuring river stage (height) and discharge (volume), lake elevations, and precipitation.

This network transmits data via satellite to a receiving station in the USGS Caribbean District office in Guaynabo. During normal operations these stations transmit every 4 hours and the data is available to the general public on the Internet ( This information is used to forecast water availability for drinking water supply and for agricultural and industrial uses.

During storm events, the stations go into an alert mode and transmit on a special channel every 5 minutes. The information received is vital for emergency decisions by the Government of Puerto Rico. As soon as the stations detect a rapid rise in the stage of the river, government officials can use the information for emergency management purposes.

At Lake Carraízo (Lago Loíza), an entire network has been designed to collect precipitation data that is fed into a hydraulic streamflow routing model to generate hydrographs at different stations upstream of the reservoir so that the Puerto Rico Aqueduct and Sewer Authority (PRASA) will be able to predict how much water will enter the reservoir and thus determine the release that must be made from the dam. This is very important because lake Carraízo is the major public water supply source for the San Juan metropolitan area.

The USGS has developed a robust system through the use of a cooperative agreement with the Civil Defense. The system consists of emergency power generators, a digital receiving ground station (DRGS), a dependable backup system at the USGS National Headquarters in Reston, Virginia, and a highly trained and dependable workforce. Before Hurricane Georges approached Puerto Rico, all USGS stations were checked to ensure that they were completely operational and ready for the storm.

During the hurricane, Computer Specialist, Dianne Lòpez-Trujillo, remained in the Caribbean District office to monitor the computer system and respond to any request from the emergency unit at PRASA and Civil Defense. Civil Engineer, Mario L. Oliveras, was stationed at the Civil Defense Headquarters with a portable computer with access to the USGS mainframe computer.

When the full impact of the hurricane hit San Juan, the satellite dish of the DRGS broke and the direct link from the remote USGS stations was lost. Fortunately, the backup system at USGS National Headquarters in Reston, Virginia, provided the information that was critical to operate the Carraízo reservoir. Lòpez set up communications with USGS Headquarters and, with the help of the Caribbean District's Surface-Water Specialist, Heriberto Torres-Sierra, was able to give information about the expected peaks to PRASA's Emergency command Center. The information was essential for PRASA officials to determine when and how much water would be released from Lake Carraízo.

The USGS network was minimally affected by Hurricane Georges. Only 12 stations, or less than 10% of the total, were damaged by the storm. After the storm, the USGS sent crews out to measure high water marks in order to quantify the flood peaks, assess damages, repair the stations, and fully document the effects of the storm. The acquisition of flood marks is important for development of accurate flood maps which are prepared to prevent future life and property losses from similar events.

Preliminary hydrologic information indicates that floods of moderate to severe intensity occurred throughout Puerto Rico. Flood discharges with recurrence intervals from 25 to greater than 100 years were registered within the basins of the Río Camuy, Río Grande de Arecibo, Río Grande de Manatí, Río de la Plata, and Río Culebrinas.

*Color maps of the path of Hurricane Georges over Puerto Rico and the location of meteorological stations on the island are available on the World Wide Web at:

As the nation's largest water, earth and biological science, and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation and the economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources
This press release and in-depth information about USGS programs may be found on the USGS home page: To receive the latest USGS news releases automatically by email, send a request to Specify the listserver(s) of interest from the following names: water-pr; geologic-hazards-pr; biological-pr; mapping-pr; products-pr; lecture-pr. In the body of the message write: subscribe (name of listserver) (yourname). Example: subscribe water-pr joe smith.

U.S. Department of the Interior
U.S. Geological Survey
651 Federal Drive, Suite 400-15
Guaynabo, PR 00965

US Geological Survey

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