WSP03104

• File Number: 8143.600
• Description: John Martin Reservoir
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 7/31/1981
• Title: RESSYM - A John Martin Reservoir System Simulation - written in CDC Fortran Extended Vers. 4
• Water Supply Pro - Doc Type: Report/Study

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MathematIcal method and theory

Given the averaye daily outflow and end of thu day cuntents
for John Martin Reservoir, the inflow may be expressed as

1 = 0 + 65

(1)2

Where

I = inflow (also average for the day)
o = outflow
65 = change in storage (contents).

The terms 0 and 65 iJre measured. Thc term 1 is therefure computed.
If the reservoir seepdye losses are assumed to be negLigible,
the evaporation may be indicated as a part of 65 by the relation

65 = I - [0+ (E v) ]

(2 )

which simplifies to

65 =I-O-Ev

( 2 - 1 )

where

Ev = evaporation

It can be seen from equatIon 2 that the quantity [O+(Ev)] is
the total outflow. The quantity Ev is in additon to the measured
outflow. Because the quantity equivalent to the evaporation i5
unaccounted for, the evaporation as qUdntified in equation 2-1 is
effected as a negative inflow. This can be exempiified under the
following special conditions:

a)
".b)
hence c)

the evaporation is in excess of the actual inflow
the change in storage is greater than the measured outflow
the inflow as computed by eq. 1 will be negative.

In reality, the seepaye losses of John Martin Reservoir are
probably very small when compared to the total water lost by
evaporation. The actudl evapordtion, therefore, can only be
dccurately determined by the application of pdn evapuration data to
compute totdl lake evapordtion.

If the historical operdtion of John Martin Reservoir were
emuldted thruugh a set of operating criteria ur principles, it Cdn
be seen from the above that the differences betweun actual
evapordtion losses dnd those dttributable to the operdtiny criteria
will be small given the degree to which the operating criteria
emulate the historical operation. This would be true because the
evaporation of the conservation pool, assumed to be described
accurately in the term 65, is determined by the contents of the
conservation pool and the emulation desired will correspond to the
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