WSP12125

• File Number: 8102
• Description: Arkansas River Hydrology
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 1/1/1997
• Author: USGS
• Title: Description of the Program Changes - 1989-97- and a User Manual for a Transit-Loss Accounting Program Applied to Fountain Creek Between Colorado Springs and the Arkansas River-Colorado
• Water Supply Pro - Doc Type: Report/Study

OJOH 1

Program Modularization

The original accounting program consisted of a
main program and fi ve subroutines. In analyzing the
program code (0 determine (I) what changes would be
needed to account for the TRF diversions and the addi-
tional TRF source and (2) where the program code
would need to be changed, it became obvious that the
changes could be made more easily if the program
were modularized. Thus, many aspects of the data
input, computational procedures, and data output,
especially the repetitive processes, were recoded into
individual subroutines. Descriptions of this recoding
or of the resulting s\lbroutines is not necessary for the
purposes of this report; however, the modularization
process and the program changes resulted in an
accounting program having 26 subroutines. During
this process, a complete list of all the program vari-
ables was created and some variable names were
changed to mal\.e them more descriptive. Modularizing
the program code and creating the variable list
provided a better understanding of the program code,
especially for persons just beginning to learn the
program, and made the task of changing the program
much simpler.

Changes to Account for Diversion of
Transmountaln Return Flows

To account for the diversion of TRF's, the
primary change needed in the accounting program was
to provide a mechanism to specify a TRF diversion al
a specific location. A diversion ofTRF could be easily
specified at any of the noMs, using a method similar to
how the NSF diversions are specified. However, the
purchaser of a TRF for diversion must incur the transit
loss for the diverted TRF, from the point of discharge
(at the CCS WWTF) to the point of diversion. Also,
the quantity of TRF to be diverted needs to be known .
prior to the actual diversion, which makes the needed
program changes more difficult. Consider this
example:
On Monday, the water commissioner is noti-
fied by a ditch owner along Fountain Creek
of an intent 10 purchase and divert
5 ft3/s of TRF for 5 days beginning on
Tuesday. Because of transit losses from the
CCS WWTF downstream to the ditch
diversion point, there. are two possibilities:
(I) The dilch owner can purchase and

,.'

divert the equivalent of 5 ft3/s per day at the
CCS WWTF, in which case the quantity of
TRF available at the diversion point is not
known until after the diversion has been
made; or (2) the ditch owner can purchase
and divert the equivalent of 5 ft3/s at the
ditch diversion point, in which case the
TRF purchase quantity needed at the CCS
WWTF is not known until after the diver-
sion has been made.
For purposes of water administration and for a
capability that could be added easily to the accounting
program, the second possibility just described was the
best option. Therefore, the program was changed to
account for diversion of a specific quantity ofTRF at a
given node (an NSF or a TRF diversion point) by
calculating the quantity of TRF that would need to be
purchased at the CCS WWTF for the specified TRF
diversion. The TRF purchase quantity is derived by
the following additional computation steps in the
subreach computations:

I. Transit-loss computations for the total quantity of
TRF are identical to the computations in the orig-
inal accounting program (fig. 5).

2. If a s\lbreach has a specified TRF diversion, the
program computes the ratio of the TRF diversion
quantity to the total TRF quantity at the upstream
node of the subreach.

3. The program assigns a proportion of the total transit
loss in the previous (upstream) subreach to the
TRF diversion quantity on the basis of the ratio
computed in step 2.

4. The program adds the transit-loss proportion
computed in step 3 to the specified TRF diver-
sion quantity, resulting in an estimate of the TRF
purchase quantity at the upstream node of the
previous subreach.

5. The program computes a new ratio between the
TRF purchase quantity just estimated and the
total TRF at the upstream node of the current
subreach and then returns to computation step 3.

6. The program repeats computation steps 3-5 for
each upstream subreach, but the ratio from step 5
rather than the ratio from step 2 is used in the
subsequent step 3 computations. The TRF
purchase quantity changes in each subreach as
the comp\ltations proceed back through subreach
I, at which point the TRF purchase quantity

\::"

CIIANGES 'TO 'TilE 'TRANSIT -LOSS ACCOUMllMG PROGRAM OURIMG 1991-92 15

.. ,
,..
,:,