8261

• UCREFRP Catalog Number: 8261
• Author: Thompson, K. R.
• Title: Annual Suspended-Sediment Loads in the Green River at Green River, Utah, 1930-82.
• USFW Year: 1984.
• USFW - Doc Type: Water-Resources Investigations Report 84-4169,
• Copyright Material: NO

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After review ing the records and other factors that may have influenced the
reliability of the records, the fallowing oonplusions have been made:
1. The cableway was a qood site for the collection of susperrled-sediment
data.
2. Sampling at the highway bridge (mostly by daily observers) was
affected by the bridge structure. The data obtained at the highway bridge,
however, were correlated with data collected at the cableway during record
carputation.
3. The data collected prior to October 1945 were not as representative
of actual conditions as were data collected later. Data collected after
October 1945 reflect more reliable and accurate sampling with the u.S. 0-43
and subsequent depth-integrating samplers.
4. Not enough samples were collected during a storm to define susperrled-
sediment loads without extrapolation. A large p1I't of the sus~nded-sediment
loads commonly is transported during storms.
Based on the foregoing oonclusions, the suspended-sediment records for station
09315000 are considered to be fair prior to 1945 and good for the remaining
period of record.

SUSPENlED-SIDlMEm' I.OAOO

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Arumal Suapended-Sediment IDads. 1930-82

Armual suspended-sediment loads for 1930-82 at S14tion 09315000 are shown
in figure 2. The annual suspended-sediment load varied considerably. The
minimum and maximwn annual loads occurred within 3 years of each other--the
minimum of 1,780,000 tons--during 1934 and the maximum of 43,400.000 tons
during 1937. The mean annual suspended-sediment load for 52 years was
15,630,000 tons, with a standard deviation of 10,800,000 tons. The minimum
daily suspended-sediment load of 54 tons was on September 27, 1956, and the
maximlUD. daily load ot 2,230,000 tons was on July 11, 1936.

A change in the volume and variability of annual suspended sediment is
apparent from figure 2. The annual volume and variability of suspended-
sediment load was greater during 1930-63 than during 1964-82. The mean load
for 1930-63 was 19,500,000 tons per year, with a standard deviation of
ll,45ll,000 tons per year, whereas the mean load for 1964-82 was 8,700,000 tons
per year, with a standard deviation of 4,000,000 tons per year. Little change
in mean annual stream disdlarge occurred between the same two periods (fig..
3), with a mean of 3,930,000 acre-feet for 1930-63 and 4,080,000 acre-feet for
1964-82. However, variability is greatly reduced in the latter period. '!his
indicates that manges in the mean annual stream disdlarge alone did not cause
the aPI8rentdlange in annual suspended-sediment load.

The double-mass curve in figure 4 provides further evidence of a change
based on the concept that "A break in the slo~ of the double-mass curve means
that a change in the oonstant of proportionality between the two variables has
occurred * * * and * * * indicates the time at whidl a change occurs in the
relationship between the two quantities." (Searcy and Hardison, 1$0, p. 33).
A break in the slo~ of the double-mass curve occurred approximately between

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