WSPC00985

• File Number: 8283.100
• Description: Colorado River Computer Models - Colorado River Simulation System - Reclamation - CORSIM
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 5/1/1985
• Author: DOI-BOR
• Title: CRSS - Colorado River Simulation System - System Overview
• Water Supply Pro - Doc Type: Report/Study

0017J6

12. Comparison with Historical Data

This section presents the procedures and results of a model verification
study. The study consisted of comparing historical flow and salt data
with flow and salt data output from a CRSS computer run. The purpose of
the study was to verify accuracy of the data and assumptions used in the
CRSS, and to provide insight into the areas of the data files and model
that may need improvement or adjustment.

12.1 Data and Procedures

The period chosen to compare historically recorded flow and salt values
with CRSS simulated flow and salt values is 1968 to 1983. The advan-
tages for choosing this period are (1) all reservoirs modeled by the
CRSS are operational, (2) the available historic data is continuous, and
(3) the period is sufficiently long enough to span a wide range of
naturally occurring hydrologic events. The main disadvantage is that
this period includes the filling of Lake Powell.

Historically recorded flow and salt data were taken from the "Quality of
Water Progress Reports." Simulated flow and salt data were generated by
the CRSM. The hydrology input data used in the simulation were the
natural flow and salt hydrology data base for the period 1968-1983. It
should be noted that the 1981-1983 data are provisional at this time.

Depletions for the simulation were taken from the "Colorado River System
Consumptive Uses and Losses" reports. The annual values given in the
reports were averaged for the Upper and Lower Basins, and the average
values were entered into the CRSM as constant values over the 1968-1983
period. Upper Basin depletions were held constant at 3,047,000 acre-
feet and Lower Basin depletions were held constant at 6,133,000 acre-
feet. In addition to the above depletions, 514,000 acre-feet of
depletions were scheduled for native vegetation and losses from the
Senator Wash Dam, Reservoir, and Pumping-generating facility; and
1,515,000 acre-feet of depletions were scheduled for delivery to Mexico.
Evaporation is not included in the depletion schedule since it is
accounted for by the CRSM.

Bank storage computations at Lake Powell were modified to more accu-
rately reflect what occurred during the filling period. Change in bank
storage was modeled at a rate of 15 percent of the change in reservoir
contents for 1968-1979, and at a rate of 8 percent for 1980-1983. The
bank storage rate modeled at Lake Mead was 6.5 percent.

Initial reservoir contents were set equal to the contents historically
recorded on December 31, 1967. Initial reservoir salt concentrations
were set equal to the salt concentrations historically recorded during
December 1967, in the river below each reservoir. . No surplus strategy
was used during the CRSM simulation. In order to more accurately simu-
late the historical release patterns caused by day to day operations of
the river system, the monthly reservoir contents in the CRSS simulation
were forced to match the historically recorded end-of-month contents.

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