WSPC00040

• File Number: 8272
• Description: Colorado River - Colorado River Basin Salinity Control Program - CRBSCP
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/28/1995
• Title: Functional Requirements Document for PRSYM - CRSS Modeling of Total Dissolved Solids - Draft
• Water Supply Pro - Doc Type: Report/Study

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therefore, the greater the depletion, the greater the con-
centration of the return flow. The concentration of the
return flow is also dependent on any salt pickup
specified in the demand data input file. An irrigation
project which is leaching salts, for example, will have a
positive salt pickup and a water quality improvement
project will have a negative salt pickup. A positive salt
pickup will increase the concentration of the return flow
and a negative salt pickup will decrease the concentration
of the return flow.

The concentration in the river at a reservoir is the con-
centration of the release. The concentration in the river
increases if the concentration of the reservoir inflow is
greater than the concentration of the reservoir. The con-
centration in the river decreases if the concentration of
the reservoir inflow is less than the concentration of
the reservoir. The concentration in the river is further
altered by the movement of water in and out of bank stor-
age and by evaporation. The evaporation of water is 'a
loss of water with no loss of salt.

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Figure 10.1 shows an example of the salt routing process.
At a diversion point, concentration in the river ~s com-
puted by taking the current flow in the river multiplied
by the current concentration in the river, subtracting the
flow in the diversion multiplied by the concentration of
the diversion, and dividing by the new flow in the river.
The concentration in the river at an inflow point is pom-
puted similarly except the terms are added instead of
subtracted. The concentration of a return flow is equal
to the concentration of the diversion multiplied by the
ratio of the diversion flow to the return flow.

10.3 Reservoir Mixing

The CRSM assumes that the reservoirs are of uniform salin-
ity, and completely mixed at all times. While this is not
completely accurate, the difference between this assump-
tion and correlating inflow to outflow through a lag
function is small. This was verified as applicable to
Lake Mead on a monthly basis by Dr. John Hendrick in his
Ph.D. dissertation (1973), Colorado State University.

The concentration in a reservoir is based on the volume of
the inflow, the volume of the release, the concentration
of the inflow, and the concentration in the reservoir at
the beginning of each month. The model has an algorithm
which determines the concentration of the re~ervoir re-
lease by weighting the current month's and previous
month's reservoir concentrations. This release quality is
equivalent to that which would occur from a constantly
mixed reservoir with a uniform inflow rate.

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