PROGRAMS AND PLANS--Frequency of Levels at Streamflow Gaging Stations. In Response Reply To: WGS-Mail Stop 415 February 28, 1990 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 90.10 Subject: PROGRAMS AND PLANS--Frequency of Levels at Streamflow Gaging Stations. The present recommendation for the frequency of levels at streamflow gaging stations is that they be run at least every 3 years (Kennedy, 1988, p. 20). There are many stations that are located in stable areas for which levels could be run less frequently. This memorandum discusses guidelines for when less frequent levels may be run. The guidelines for levels frequency given by Kennedy (1988, p. 20) are to be followed unless it can be shown that the station is stable. Stability involves the well and shelter, staff gages, wire-weight gages, reference points, and reference marks. If any of these items is unstable, then Kennedy's recommendations are to be followed. If after at least 5 sets of levels over a period of at least 10 years, the gaging station is shown to be stable, a lesser frequency of levels may be adopted. Level summary sheets should be prepared for all gages to provide for easy determination of gage stability. A recommended summary sheet format is shown in Figure 18 of the report by Kennedy (1988) and a form for this purpose that can be copied for District use is located on the last page of Kennedy's report. The OSW recommends that levels at regular gaging stations be run at least every 5 years if stability is shown to exist. It is also recommended that levels at crest-stage gages be run at least every 3 years. Additional levels may be needed if a major flood, or other event, occurs that could disturb some part of the gaging station. As a matter of practice, it is also recommended that when levels are run, the station description be reviewed and updated. This is not meant to preclude updates of the station description at other times as needed. If a variance in frequency from that proposed by Kennedy (1988) is needed, a plan for frequency of levels is to be prepared by the District and kept in the District files. The District policy for frequency of levels should be made a part of the District's quality-assurance plan. REFERENCE Kennedy, Edward J., 1988, Levels at streamflow gaging stations: U.S. Geological Survey open-file report 88-710, 42 p. Charles W. Boning, Chief Office of Surface Water WRD Distribution: A, B, S, FO, PO This memorandum does not supersede any previous memorandum.