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.! '.; GJHHG >.. essence, subreach I (SRI in fig. 2 and in table I) from the original hydrologic system was divided into two subreaches (SR I and SR2 in fig. 6 and in table 4). The physical and hydraulic characteristics of the new subreaches (SRI and SR2 in fig. 6) were derived by proportioning the characteristics (Kuhn, 1988, p. 14-20) of the original subreach (SR I in fig. 2); the remaining subreaches and nodes also were renum- bered (fig. 6 and table 4). Therefore, the transit-loss computations were identical to those for the ori ginal program, except for one additional stream-segment and one additional subreach computation (figs. 4 and 5). Including station 07105530 in the accounting program would improve calculation of transit losses because mosl of the NSF gains and losses that were prorated originally between stations 07105500 and 07105800 (nodes A and B in fig. 2) actually occur between stations 07105500 and 07105530 (nodes A and B in fig. 6). Changes to Account for Transmountain Return Flows from the Fryingpan- Arkansas Project ., ..'~ ;~:L <~ In the stream/aquifer model (Land, 1977), computations can be made only for two streamflow entities; in the transit-loss study (Kuhn, 1988). the entities were TRF and NSF. IIi the accounting program, computations also can be made only for two streamflow entities. The changes to the accounting program that were needed 10 enable accounting of FAP TRF's required computations for three stream- flow entities-CCS TRF, FAP TRF, and NSF. To enable accounting of the two TRF entities, the accounting program was changed to provide dual transit-loss computations--one set of computations would be for the CCS TRF's and one set of computa- tions would be for the FAP TRF's. For each set of computations, all streamflow other than the TRF being considered (CCS or FAP) was assumed to be NSF. This method was agreed on by all the agencies involved in applying the accounting program (Gerhard Kuhn, U.S. Geological Survey, written commun., 1995). The modularization of the program during the 1991-92 changes greatly facilitated implementing the changes needed to account for the CCS and the FAP TRF's. In the 1991-92 program changes, the actual transit-loss computations [the stream-segment and ,:,. .:. subreach computations (figs. 4 and 5)] for the CCS TRF's were contained in a primary subroutine that used five additional subroutines for the various components of the transit-loss computations. The primary subroutine that computed the transit losses for the CCS TRF's was duplicated to compute. transit losses for the FAP TRF's. These changes, and other changes required during the 1994-95 revisions, resulted in additional modularization of the accounting program; several subroutines for obsolete or unused functions also were removed from the program. When completed, the changes made during 1994-95 resulted in a program with 30 subroutines. In the revised program, the primary transit-loss subroutines, one for the CCS TRF's and one for the FAP TRF's, used seven additional subroutines for the various components of the transit-loss computations. To enable accounting of the FAP TRF diver- sions, the same methods thai were implemented in the 1991-92 changes to account for the exchangeable CCS TRF diversions (see the "Changes to Account for Diversion of Transmountain Return Flows" section, p. 15-16) were used to account for the FAP TRF di versions. Changes to Acc!)unt for Additional Diver- sions of Transmountain Return Flows from Colorado Springs The changes made to the accounting program during 1991-92 enabled accounting of the CCS TRF diversions that were exchanged for equivalent quanti- ties of FAP water stored in Pueblo Reservoir. For the 1994-95 changes, the CCS wanted to enable accounting of an additional category ofTRF diversion that would not be exchanged. To enable accounting of the nonexchangeable diversion category, the same methods that were implemented in the 1991-92 changes to account for the exchangeable diversion category (see the "Changes to Account for Diversion of Transmountain Return Flows" section, p. 15-16) were used to account for the nonexchangeable diver- sion category. Changes to Program Output The 1994-95 changes 10 the accounting program resulted in a program that would account for 20 Descriptions 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 f Colorado