WSP04876

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1983
• Author: USDOI
• Title: Quality of Water - Colorado River Basin - Progress Report No. 11 - January 1983
• Water Supply Pro - Doc Type: Report/Study

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PART VI.
AND

EVALUA TlON OF HISTORICAL TRENDS
PRESENT SALINITY CONDITIONS

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The Bureau of Reclamation has embarked on a major analysis of
long-rem salinity and specific ion trends. The analysis of trends
contained in some 70 years of water qual iry records is possible with the
extensive use of computers. Accordingly, the past 6 years have been
devoted to digitizing water quality data and developing computer programs
to reanalyze the entire record. This computerization, which is still in
progress, is essential to understanding the long-term salinity trends
throughout the recorded ....ater quality history of the basin. The ongoing
studies described in Part IX are largely directed to a better understand-
ing of the relationships bet~en land use, water use, hydrology, chemical
and biological mechanisms, and long-term salinity trends.

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Although this report provides a 2-year update of observed conditions
1n the basin, the goal is to understand the long-term trends and to then
be able to accurately predict the near- and long-term future sal inity at
various levels of depletion and development. The CRSS model presented
in Part VII predicts future salinity trends given expected depletions and
salt loading schedules. Reclamation is also now using the canputer
extensively for long-term specific ion analysis and reservoir studies to
improve these predictions.

A. Quality of Water Records

The evaluations of the historical sal inity in the Colorado River
Basin are based on streamflow records at selected stations as sho\olll on
Figure II-I. The basic data summarized in this report I.If're obtained
primarily from the USGS and were funded in part by Reclamation.

Salt loads and concentrations were generally calculated from daily
conductivity and flow records. Correlations were used at each station to
convert conductivity data to salt concentrations. I.'here records were not
available, missing data were estimated by the use of correlations with
other parameters or ....ith other nearby stations.

Historical steamflow, salinity concentrations, and salt load data
for the 20 key stations for the 1941-80 period of record are presented in
Tables I to 20 at the end of this report. The average concentrations and
loads were determined on a flow-weighted basis using daily data whenever
possible. Some small differences (-d,ODD acre-feet/yead in discharges
from USGS rt'!cords ~re noted and pr;-surnably occurred due to differences
in rounding within the computer programs used.

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B. Historical Analysis of Salinity

A trend analysis was made for two key stations in the lower basin to
determine if, in the past, there have been significant changes in T05,
and Iohat the range of fluctuations in TOS have been. A standard linear

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