WSPC04476

• File Number: 8283.200
• Description: Colorado River Basin-Colorado River Computer Models-Colorado River Decision Support System-RAY
• State: CO
• Water Division: 5
• Date: 12/29/1993
• Title: Hydrosphere-Colorado River Model-Technical Overview
• Water Supply Pro - Doc Type: Report/Study

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UU2.110

Hydrosphere's Colorado River Model

December 29, 1993
Page 17

The assumptions in the model governing reservoir operations reflect the current
operating criteria. The model allows limited modification of reservoir operations via changes
in storage.targets, release requirements, flood control space requirements and relative storage
priorities. Future versions of the model may incorporate more flexibility to change operations;
these modifications will be highly dependent on the types of analyses sought by our customers.

Hydropower Generation

In its current configuration, Hydrosphere's Colorado River Model does not consider
hydropower outputs in deterrnining water allocations. The model calculates energy production
ex post as a function of (I) the amount of water that passes through the turbines, (2) the feet of
effective head that the water drops, and (3) power plant efficiency, generator capacity, and
turbine capacity. For each hydroelectric dam, energy production for time period (Le., month)
i in kilowatt hours (KWH) is computed as:

KWH; = Hi . Qi . Efi . C

11)

subject to
H. EPi - Et (2)
1
H' >= Hm (3)
1
KWHi <= Mg (4)
Q. <= Mt {51
1
where:
H = head in feet at beginning of period
Q = flow in acre-feet per month
Ef = generator efficiency
Hm = minimum head for intake
Mg = maximum generator capacity in kWh per
month
Mt = maximum turbine capacity in acre-feet
per month
Ep = pond elevation in feet
Et = tailwater elevation in feet
C = a constant to convert from acre-feet to kWh
Evaporation

Reservoir evaporation is computed at the end of each month from surface area/volume
relationships and unit evaporation rates adopted from the USBR' s CRSM control file (USBR,
1991).

Salinity

Salinity concentrations, expressed in parts per million, are calculated at the end of each
month in Hydrosphere's Colorado River Model. The concentration is computed by
considering natural salt sources, the percentage of each diversion which returns to the system
as return flows, the salt concentration of the return flows and mixing at the reservoirs.
Previous applications of the model have required salinity concentrations below Lake Mead
only. The commercial version of the model will provide salinity concentrations at two

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