Water Supply and Irrigation Papers of the United States Geological Survey . on and correcting the observedgage heights to what they presumably would have been were the bedand banks of permanent material. First, it is assumed that thechanges occur at a fairly uniform rate between times of successivemeasurements. This assumption necessitates measurements at criti-cal times when the rate of change is not uniform. As an exampleof the effect of a shifting bed on the relation between gage heightsand discharge, two gagingsmade in 1903 on Loup River at Columbusmay be given: March 20, gage height
Water Supply and Irrigation Papers of the United States Geological Survey . on and correcting the observedgage heights to what they presumably would have been were the bedand banks of permanent material. First, it is assumed that thechanges occur at a fairly uniform rate between times of successivemeasurements. This assumption necessitates measurements at criti-cal times when the rate of change is not uniform. As an exampleof the effect of a shifting bed on the relation between gage heightsand discharge, two gagingsmade in 1903 on Loup River at Columbusmay be given: March 20, gage height feet, discharge 6,074second-feet; May 7, gage height feet, discharge 3,409 forty-eight days the bed of the stream so changed that for the samegage heights the discharge was only about half as much as at theearlier measurement. Suppose that the bed of the stream was not subject to fluctuations,and there was available a rating table prepared on this basis, giving METHODS OF STREAM MEASUREMENT. 11 1 „„1 L,.„..L.,.., ,J .,.,1 .J I s-Tio Gage rod. 12 SURFACE WATER SUPPLY OF NEBRASKA. the discharge of the stream for all gage heights. Taking the dis-charge found on March 20 above and entering such a rating table,we find the gage height required to give this discharge. The differ-ence between the observed gage height and that taken from the ratingtable is the correction to be applied to the gage heights for that the correction is the distance between any plotted pointof measurement and the curve, measured parallel to the gage-heightaxis, plus if the point falls below the curve and minus if above. Ina similar manner the correction for the measurement of May 7 isobtained. No flood occurred between these dates (see gage heights,pp. 122-123), and there is no reason to believe that changes in the 6-0 •s • i • i / •• • •• / • • •» ?•• ••• • •• •• • • /« • y ••• J» •
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