WSP11333

• File Number: 8273.100
• Description: Colorado River Basin Salinity Control - Federal Agency Reports - BOR
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 5/1/1975
• Title: Application of Stochastic Hydrology to Simulate Streamflow and Salinity in the Colorado River
• Water Supply Pro - Doc Type: Report/Study

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through 19~5 with the 1965 level of depletions, Information compiled
in Comprehensive Framework Studies was used as a basis for establish-
ing the means at major streamflow stations, Below Hoover Dam, the
data used ~ere those subsequent to 1960 when deliveries to Mexico were
reduced to, about 1.5 million acre-feet in anticipation of the closure
of Glen Cahyon Dam and which reflect a relatively homogeneous condi-
tion, The values obtained were then adjusted to reflect a 1970 level
of development, As completed, the data used for the model primarily
represent ~ean streamflow for the 1914 to 1965 period modified to
reflect a 1965 level of development and the 110,000 acre-foot diversion
of the San;Juan-Chama Project in the Upper Basin, and a 1970 level
of development in the Lower Basin, As used in the simulation model,
these data, therefore require that all projected depletions in the
Upper Basin reflect the amounts beyond the 1965 level (except for
San Juan-Chama which is provided for in the data) and those for the
Lower Basi~ the amounts beyond 1970.

Adpustment of Means

The general pattern of the change in the means of streamflow due to
man's activity would be to reduce the values during high flow periods
and slightiy reduce or maintain those of low flow periods, Time
limitation~, however, precluded an extensive effort to determine just
how the monthly means of each station should be adjusted to reflect
man's acti~ity, Therefore, the approach used for the present data
base was to adjust the means by the same factor throughout the year,
In the approximate fashion, this constant factor approach is in the
right direction, but the results should not be considered as an exact
estimate of the means.

3.2.1

For quality, besides the adjustment needed to reflect man's activities,
there is also a need to modify the data to reflect the same flow
conditions'portrayed in the adjusted streamflow data. Time trends
of the residuals of the correlations between the random components of
flow and q~ality were computed for some of the stations in the Upper
Basin to d~termine if the quality means should be increased to
represent the 1965 level of quality. Rather than showing a deteri-
oration of:quality with time, the trends showed either no change or a
slight improvement. From these results it was concluded that the
means for the period of record would provide a good representation of
present-day quality in the Basin and that an adjustment to the data
to reflect man's activities was not needed, However, the data do
show that ~here is an inverse relationship between flow and quality -
the quality concentrations are smaller during high runoff years and
months, an9 larger during low runoff years and months. Since the
mean strea~flows of the period for which quality data are available
are generally lower than the mean streamflows portrayed in the adjusted
streamflow1data, the inverse relationships were used to adjust the

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