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USGS National Streamflow Information Program

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Trends in the Size of the USGS Streamgaging Network

With the considerable interest in the USGS streamgaging program, we wanted to relay some of the latest statistics on the status of the network. It takes a while after the end of each water year for all of our offices to finalize the data and only then are counts completed. Here are a few facts.

From Water Year 2008 to Water Year 2009, the total number of streamgages operated by the USGS decreased by 47 streamgages to 7,825 streamgages. For reference, the greatest number of streamgages that have ever been operated in any given year was 8,320 streamgages in Water Year 1968.

One of the things the USGS tracks with great interest is the status of our "long-record" streamgages. These are defined as streamgages with 30 or more years of record. From Water Year 2005 to Water Year 2009, we had 384 long-record streamgages discontinued.

The number of losses of long-record streamgages has risen steeply in the past few years. It hit a low of only 22 losses in Water Year 2001, the year in which Congress provided a large funding increase for the National Streamflow Information Program. Since 2001, annual losses of long records streamgages have been as high as 105 streamgages.

Decisions to cease operations of streamgages are always undertaken with great care and in consultation with others. The factors that figure into the decision are the availability of funds from USGS appropriations and from the 850 Federal, State, and local partners who contribute to the network and our costs, which rise with mandated increases in Federal pay scales. Factors that enter into these decisions include importance of the streamgage to flood hazard mitigation, water resources operations, and long-term characterization of regional hydrologic systems.

In summary what we are seeing in the past few years is a significant acceleration of the losses in the network similar to what we observed in the mid-1990's. The increased Federal funding of 2001 resulted in a brief turn-around but the losses are growing at the present time. The changes in the status of the network continue to be highly varied across the Nation. Some States, river basins or municipal areas are actually seeing growth in the network because of increased interests and funding from specific funding partners, while at the same time other States or river basins are experiencing rapid declines due to steep declines in the financial contributions of specific funding partners.

Graph of Number of Active USGS Streamgages from 1901-2009
Figure 1. The number of active USGS streamgages from 1901 to 2009.

Loss of Long-Term Streamgages
Figure 2. Number of streamgages with 30 or more years of record discontinued from 1990 to 2009.

Loss of Long-Term Streamgages
Figure 3. Number of streamgages with 30 or more years of record discontinued from 1998 to 2008.

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