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UJil435 sums the diversions for all ditches within the stream sc:gment. 6. SS_K6 (fig. 4), which is the stream-segment channel length, in miles. SS_K6 is derived from the subreach channel lengths that were deter- mined in the transit-loss study (Kuhn, 1988, table 3). The channel lengths for all subreaches within a stream segment were summed and are included in the program code. The unknown quantity in the stream-segment computation" is SS_UJ (fig. 4); the following steps are used in the stream-segment computations to derive the unknown quantity; I. Compute an initial estimate of NSF at the down- stream gaging station; this estimate is equal to SS_K4 (the total streamllow at the downstream gaging ,tation) minus SS_K2 (the TRF at the upstream gaging station) (see the "Assumptions Used in the Computations' section, p. 8). 2. Compute a revised estimate of NSF at the down- stream gaging station; this estimate is equal to SS_K5 (the total NSF diversion in the stream segment) plus the result from computation step I. The revised estimate of NSF at the downstream gaging ,tation is the conditional NSF, provided there had not been any NSF diversions in the stream segment. 3. Compute the estimated total NSF loss or gain in the stream segment; the total NSF loss or gain is equal to SS_K3 (the NSF at the upstream gaging station) minus the result of computation step 2. 4. Compute SS_U I [the estimated NSF loss or gain in the stream segment, in cubic feet per second per mile (fig. 4)J, which is equal to the result from computation step 3 divided by SS_K6 (the stream-segment channel length). When the stream-segment computations are completed, the accounting-program computations proceed to the subreach computations; the result from computation step 4 of the stream-segment computa- tions is used in the subreach computations. Because node E (fig. 2, table I) is the la"t gaging station, the stream-segment computations are not made for subreach 14 (there is no downstream gaging station to define a stream segment); therefore, NSF loss or gain is assumed to be zero in subreaeh 14 (Kuhn, 1988, p.81). ., Subreach Computations The subreach computations are. diagramed in figure 5; to perform the subreach computations, the following subreach known quantities (SR_Kx, where x is a number) need to be defined: 1. SR_K 1 (fig. 5), which is the TRF at the upstream node. For most sub reaches, SR_K I is equal to SR_U3 (the TRF at the downstream node) from the computations for the previous subreach (fig. 5). For a subreach with the upstream node at node A I, B, C, D, or E (fig. 2; table I), SR_KI is equal to SS_K2 (the TRF at the upstream gaging station) from the stream-segment computations (fig. 4). 2. SR_K2 (fig. 5), which is the NSF at the upstream node. For most subreaches, SR_K2 is equal to SR_U I (the NSF at the downstream node) from the computations for the previous subreach (fig. 5). For a subreach with the upstream node at node B, C. D, or E (fig. 2; table I), SR_K2 is equal to SS_K3 (the NSf at the upstream gaging station) from the stream-segment computations (fig. 4); howeve.r, iftheupsueam node is node A I , then S R_K1 is equal to the sum of ( I ) the daily mean discharge at station 07105500 (node A, table I), (2) the native return-flow discharge at the CCS WWTF, and (3) the esti- mated NSF loss or gain between nodes A and A I (fig. 2; table I). The estimated NSF loss or gain between nodes A and A I is computed by multi- plying SS_U I [the stream-segment NSF loss or gain (fig. 4)] by the channel length between nodes A and A I (0.6 mil. 3. SR_K3 (fig. 5), which is the total NSF diversion between the nodes. The NSF diversions are input individually for each ditch, and the program sums the diversions for all ditches within the subreach. 4. SR_K4 (fig. 5), which is the subreach channel length, in miles. Values for SR_K4 were deter- mined in the transit-loss study (Kuhn, 1988, table 3) and are included in the program code. The unknown quantities in the subreach compu- tations are SR_U1, SR_U2, and SR_U3 (fig. 5); the following steps are used in the subreach computations to derive the unknown quantities: I. Compute the NSF at the upstream node that is to be routed through the subreach to the downstream ..j ~~.. .., ...., .... I DESCRIPTION OF THE ORIGINAL TRANSIT-LOSS ACCOUNTtNG PROGRAM 9 ....