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!~'.(,:.,:'::: ;:~,'-",::'{," ".,S~"","~",~;,:"~_;,:-~,,,;~,.,t..1t\.,:-':;.;-,..,,~.,,,-.. -~''-:,"'-''."'~,_. '.'.,,'''' ".' .,-.^",>~ ,-".,," C'J v-4 '" (- .. 32 (j C:.-.~ RIO GRANDE COMPACT COMMISSION REPORT <~~..u..",ij-, ACCURACY OF RECORDS The Rules and Regulations of the Commission state that the equip- ment, method. and frequency of measurement at each gaging station shall be sufficient to obtain records at least equal in accuracy to those classified as "good" by the U.S. Geological Survey. Within the physical limitations of stream gaging. the agencies obtaining the records. at Compact gaging stations have compiled with these regulations. The accuracy of discharge data depends primarily on (1) the stability of the stage-discharge relation, or if the control is un- stable, the frequency of discharge measurements, and (2) the accuracy of observations of stage, measurements of discharge, and interpre- tation of records. The station description states the degree of accuracy of the daily records. "Excellent" means that about 95 percent of the daily discharges are considered to be within 5 percent of true value; "good" within 10 percent; and "fair" within 15 percent. "Poor" means that daily discharges have less than "fair" accuracy. The phrase "within 5% of true value" used to qualify "excellent" records establishes the extremes of the probable errors for 95% of the days in a given period of time. The word "within" defines the range of errors with individual daily values falling between 95% and 105% of true value. The probable error in a monthly or annual mean discharge depends more on the distribution of the daily errors between these two limits than it does on the limits themselves. For this reason monthly and annual records are much more accurate than most daily records. t:~;~ ~f~j;< [.1t~~~,~~,