A rating‐curve method for determining silt‐discharge of streams

During the course of investigations of the probable rate of silting which should take place in the proposed Denison Reservoir, an attempt was made to secure a correlation between suspended load of the Red River near Denison and the discharge. Observations of the silt-content had been made at intervals since 1930, both by the United States Department of Agriculture and the United States Engineer Offices. The United States Geological Survey has operated a stream-gaging station on the Red River continuously since October 9, 1923. Moreover, the United States Weather Bureau has maintained daily river-stages since 1906 and the daily discharge-record has been extended to provide a 33-year record. A correlation between silt-discharge in tons per second and water-discharge in cubic feet per second would permit a long-time record of silt-discharge to be established. By plotting the observations on logarithmic paper a straight-line relationship was found to exist between the two variables. The graph may be called a silt-rating curve. Such a rating curve for the Red River near Denison is shown on Figure 1. The method is presented with the hope that it may be found applicable to other streams. If such be the case, the utility of the scheme would be found in (a) the extension of the silt-record prior to the time of beginning observations and (b) the substitution of periodic silt-sampling for daily sampling. Either application involves the use of daily discharge-records. The silt-and-water-discharge relationship may also be a step toward the general solution of the problem of sediment-discharge of natural streams.