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Ratings are available to agencies and other interested parties from the depot via http at the following URL: http://waterdata.usgs.gov/nwisweb/data/exsa_rat/XXXXXXXX.rdb where XXXXXXXX is the 8-15 digit USGS station number. [example: http://waterdata.usgs.gov/nwisweb/data/exsa_rat/03599500.rdb] You will be prompted to save the file to a user defined location.
Currently the depot is limited to stage-discharge ratings. For a slope station, only the base stage-discharge rating will be available and for an index-velocity station no rating will be available.
It is important to note that ratings will change, and sometimes frequently. Checking the depot regularly will ensure that the currently applicable shifted rating is used for the current data, and that the current rating cannot necessarily be used on historical data. A standard disclaimer statement at the head of each rating file is included indicating this.
"Stage-discharge relations (ratings) are usually developed from a graphical analysis of numerous discharge measurements. Measurements are made on various schedules and sometimes for different purposes. All discharge measurements are compiled and maintained in a data base. Each measurement is carefully made, and undergoes quality assurance review. Some measurements indicate a temporary change in the rating, often due to a change in the streambed (for example, erosion or deposition) or growth of riparian vegetation. Such changes are called shifts; they may indicate a short- or long-term change in the rating for the gage. In normal usage, the measured shifts (or corrections) are applied mathematically to a defined rating.
The tables being provided are shift corrected, incorporating the mathematical adjustments for ease of use by the user. The shift adjustments are applied to the individual ratings as measured data becomes available, resulting in an adjusted rating. Some ratings may change as often as weekly, others may not change for months or years.
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