WSP04095

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1987
• Author: USDOI
• Title: Quality of Water - Colorado River Basin - Progress Report No. 13 - January 1987
• Water Supply Pro - Doc Type: Report/Study

PART VIII. EFFECl'S OF DEVELQPMElIT ON SALINITY

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A.

Methods

An evaluation of the probable effects of developments on the flows and
water quality of the Colorado River Basin was made using a computer model.
The model, Colorado River Simulation System (CRSS), evaluates the impacts of
depletions, salt pickup, and salinity control on future salinity at key
stations within the basin.

CRSS is a package of computer programs and data bases developed by
Reclamation as a tool to be used by water resource managers dealing with
water-related issues and problems in the Colorado River Basin. The Colorado
River Simulation Model (CRSM), the central feature to the CRSS, is a computer
program which simulates the flow of salt and water through the Colorado River
system.

The model simulates operation of the river system on a monthly time
frame, using historical (virgin) flow records, present and future depletion
schedules, present and future levels of salinity control (optionally), and
present and future salt loading estimates to predict salinity throughout the
Basin. Salts and water are routed through the system by a simple mass balance
accounting procedure in ~TIich salinity is modeled as a conservative parameter.
Irrigation and transbasin diversions show salt gains and losses, respectively;
other uses (municipal, industrial, evaporation, mineral, etc.), with the
exception of the Las Vegas wash, show no gains in loading due to salt pickup.

Among the assumptions used is CRSS salinity projections is the routing of
salts through a given reservoir. The model routes the salts through the main
stem reservoirs using a once-a-month mixing algorithm. This assumption limits
the ability of the model to predict monthly variations in salinity; however,
it does not limit the model in predicting long-term salinity since the monthly
differences average out on a yearly basis.

A simulation of historical conditions within the basin was used to test
the ability of the CRSS to simulate flows and salinity. The results of the
test were then used to calibrate the model. Gains and losses between stations
along the Colorado were adjusted to minimize the error between simulated and
observed salinity concentration. The development and use of CRSS is an
ongoing process; however, results from the model have been favorably compared
against the 1968-78 historical conditions, and Reclamation believes that in
its present form, CRSS is the best long-range predicitive tool available.

B. Initial Salinity Conditions

For these simulations, Table VI-l summarizes the estimated present and
projected future development used in CRSS through the year 2010 for the Upper
Basin and the Lower Colorado mainstream of the Colorado River. The virgin
flow data base used included monthly flow data for 1906-83. The mean virgin
flow for this period was 15 million acre-feet per year at Lees Ferry.

VIII-1

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