Streamgage History

The U.S. Geological Survey (USGS) has been measuring the flow in the Nation's rivers since 1889. This graph (Slide 1) shows the number of active USGS continuous record streamgages in operation from 1901 through 2004. The number of streamgages in operation rose steadily from 1901 for nearly 7 decades, reaching a peak number in operation in 1968 of 8,221 active streamgages. From 1968 until 1981 the number of active streamgages fell slightly to about 7,770 streamgages, then the number declined rapidly to about 7,000 streamgages by 1984 where it stayed relatively stable for nearly 15 years until 1998 when the number of active streamgages again climbed to about 7,530 streamgages by 2003. In 2001, NSIP received a funding increase to help sustain the increasing network size, although most of the streamgages added by NSIP were reactivations of previously discontinued streamgages. Because of level funding for both NSIP and the Cooperative Water Program, and inflationary cost increases to operate streamgages averaging 3 to 4 percent, 2004 and 2005 both showed a decline in the total number of active streamgages resulting in about 7,360 streamgages active at the end of 2005.

Slide 1
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Slide 2 shows both the total active USGS streamgages from 1980 to 2005 (the blue line) and the number of streamgages designated as NSIP Federal-goal streamgages active from 1980 to 2004 (the red line). Slide 3 shows only the number of active USGS streamgages from 1980 through 2005 at a different scale than slide 2 (blue line of slide 2) showing more of the year to year variability in the number of active streamgages. A rapid decline of over 850 streamgages from 1981 to 1984 can be seen in slide 3. For the 14 year period from 1984 until about 1998, the streamgaging network was fairly stable, although declining slightly. From 1999 through 2003, the network showed a steady increase in the number of active streamgages. It was during this time that NSIP received a substantial increase in funding that helped sustain the growth in the network, although most of the streamgages added to the network with NSIP funding were reactivations of critical previously discontinued streamgages. The number of streamgages in the network declined in both 2004 and 2005 due to level funding for NSIP and the Cooperative Water Program and inflationary cost increases for operating streamgages of 3 to 4 percent per year. Slide 4 shows the number of the streamgages that have been designated as NSIP Federal-goal streamgages active each year from 1980 through 2004 at a different scale than in Slide 2 (red line of slide 2). Although the NSIP plan was not developed until about 2000, a substantial number of the streamgages that would be part of the NSIP backbone network were already in operation, funded through the Cooperative Water Program. Slide 4 shows that the number of these critical streamgages was declining at a fairly rapid rate from 1980 until 1998. This slide also shows the dramatic effect in 2001 and 2002 of the NSIP funding increase in 2001 on the growth of the number of streamgages designated to meet Federal needs. Because of level funding and inflationary cost increases, the number of NSIP streamgages started declining again in 2004 and another decrease is expected when 2005 values are all compiled.

Slide 2
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Slide 3                                                     Slide 4
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Slide 5 shows the number of USGS streamgages discontinued each year from 1980 through 2004 that had at least 30 years of streamflow record when they were discontinued. The USGS uses a value of 30 years of streamflow record to designate long-term streamgages that are more valuable for assessments of trends and of the effects of land use, water use, and climate changes. There are several important things to note on Slide 5. First is that the loss of long-term streamgages is quite variable through time. The second is that there have been recent years with losses of over 150 of these important streamgages. Third, the funding increase for NSIP in 2001 is very noticeable in the decrease of the loss of these long-term streamgages; and lastly the rate of loss from 2003 to 2004 is now approaching the higher levels of pervious years (from 56 lost in 2003 to 122 lost in 2004). Slide 6 shows the cumulative loss of these long-term streamgages shown in Slide 5. The graph shows a fairly stable rate of loss through time of nearly 78 streamgages per year and that from 1980 to 2004 2,051 streamgages with 30 or more years of streamflow record were discontinued.

Slide 5                                                     Slide 6
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Slide 7 shows how the USGS has strived to convert streamgages to deliver data in real-time, with nearly 90 percent of the USGS streamgages delivering real-time streamflow information at the end of 2004. The real-time technology used at the majority of streamgages is satellite transmission, but some streamgages are equipped with telephone or radio transmitters. Nearly all of the USGS real-time streamgages display the streamflow information on the WWW within 4 hours the measurement at the streamgage.

Slide 7
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