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<br />32
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<br />RIO GRANDE COMPACT COMMISSION REPORT
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<br />ACCURACY OF RECORDS
<br />
<br />The Rules and Regulations of the Commission state that the equip-
<br />ment, method, and frequency of measurement at each gaging station shall
<br />be sufficient to obtain records at least equal in accuracy to those
<br />classified as "good" by the U.S. Geological Survey. Within the
<br />physical limitations of stream gaging. the agencies obtaining the
<br />records at Compact gaging stations have compiled with these
<br />regulations.
<br />
<br />The accuracy of discharge data depends primarily on (1) the
<br />stability of the stage-discharge relation., or if the control is un-
<br />stable, the frequency of discharge measurements, and (2) the accuracy
<br />of observations of stage, measurements of discharge, and interpre-
<br />tation of records.
<br />
<br />The station description states the degree of accuracy of the
<br />daily records. "Excellent" means that about 95 percent of the daily
<br />discharges are considered to be within 5 percent of true value;
<br />"good" within 10 percent; and'lIfair" within 15 percent. "Poor"
<br />means that daily discharges have less than "fair" accuracy.
<br />
<br />The phrase "within 5% of true value" used to qualify "excellent"
<br />records establishes the extremes of the probable errors for 95% 'of
<br />the days in a given period of time. The word "within" defines the
<br />range of errors with individual daily values falling between 95%
<br />and 105% of true value. The probable error in a monthly or annual
<br />mean discharge depends more on the distribution of the daily errors
<br />between these two limits than it does on the limits themselves.
<br />For this reason monthly and annual records are much more accurate
<br />than most daily records.
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