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'002033 . 3. COMPUTATIONS 3.1 Computation Procedure for Quantity The basic program approach is outlined so that the user may better appreeiate the limitations and assumptions involved in using the program (see Section 6.2). Standard internal units for flow are 1,000 acre-feet/month and for reservoir volumes 1,000 acre-feet, with the corresponding salinity units of 1,000 tons/month and 1,000 tons (i.e., mass only). Only standard units are allowed for flow and volume inputs. Output is normally in 1,000 acre-feet but the user has the option of having units of lOa's, la's, or l's of acre-feet depending on the available field width. .Salinity mass can be similarly scaled on output. Salinity inputs and outputs may also be expressed as concentrations: either ppm or tons/acre-foot. Non- standard input units are converted to standard ones prior to com- putation. Standard ones are converted to requested nonstandard units prior to output. It is assumed that the river flows are independent of salinity. The program first computes flows and reservoir releases, and then computes the corresponding salinities. . Computations commence with the first upstream boundary referenced on input (internal subscript 1) and proceed downstream until a junction is encountered. The computation procedure is now restarted at the second upstream boundary, proceeding as before until a junction is encountered. Since this may not be the same junction initially eneountered, the program checks to see if all upstream branches into the junction have been entered. If they have, computations proceed downstream until either another junction or the downStream boundary is reached. If all branches were not entered, the next upstream boundary is used as the starting point for continued computations. When a river reach element is encountered, the net effect of the import/export, irrigation, and export volumes is computed. The sequence of inputs within the reach is unimportant with only their aggregate value considered. This limits the obtainable resolution of the results. If more detail is necessary, the reach must be sub- divided into smaller reaches containing the appropriate inputs. An internal sign eonvention in which a depletion of flow is negative and an accretion is positive is attached to the aggregate value. This is algebraically added to the upstream inflow to the reach resulting in the computed downstream outflow. If the outflow is negative, the total streamflow has been depleted. The negative outflow now represents the additional demand placed upon the system. . (rev. 07/75)