Point Flow Analysis Software for the Lower South Platte River

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� I POINT FLOW CALCULATIONS Point flow calculations can be performed to varying degrees of complexity. It is fundamental that users of this point flow software, as well as users of the ensuing generated databases, fully recognize the theory utilized within the computations, the limitations of such theory, the implied assumptions, and the ramifications of these assumptions. The objective of this section will be to examine the underlying methodology and familiarize users to the capacity and limitations of the point flow calculations. Although the name 'point flow' implies that the only outcome from such calculations is a value defining the river flow at a given point, other information results which is of equal importance. The unaccounted gains to, or losses from, the river are additional values computed in a 'point flow' calculation. Therefore, throughout this document the term 'point flow calculation' or 'point flow study' entails the determination of both point flows at defined locations along the river an the gains within defined river reaches. Prior to delineating the methodologies used for the point flow calculations, certain terms commonly used in the User's Guide deserve additional clarification. Listed alphabetically, these terms include: • flow directly above and /or directly below - The river channel flows calculated by the point flow software are location specific and are defined as being at a point in the river either directly above a structure or directly below a structure. Therefore, the flow directly above refers to the flow in the river channel immediately before river 'transactions' (inflows and /or diversions) occur at a structure point, while flow directly below refers to the flow in the river channel immediately after a river transaction. Furthermore, the flow directly above a structure can be viewed as the river flow exiting the river subreach directly up river of the structure, whereas, the flow directly below a structure can be viewed as the river flow entering the river subreach directly down river of the structure. • gain - The unaccounted influxes to the river are termed river gains. The unitary basis for river gains will be cubic feet per second per river mile and is assumed to remain constant between any two consecutive structures (nodes). Negative river gain values denote the occurrence of unaccounted river losses. The point flow calculations and software are both written in terms of ± gains rather than + gains and + losses. Gains to a river 'system', (either positive ( +) or negative ( -)), can be attributed to many occurrences including: unaccounted surface inflows, changing river bank storage, and underflows from the tributary aquifers. • node - See structure. • point of dry river - During periods of peak river demand certain canals or ditches may divert the entire flow of the river (less river dam loss). Although such an event may not result in a truly 'dry' river surface, it is assumed that for such instances the flow in the river immediately following the diversion structure is essentially zero (0). Points of Dry River can only be determined by observing the river channel directly below a diversion structure. This is 3 ptflguid.wpd