Point Flow Analysis Software for the Lower South Platte River

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Beginning from the most up river reach boundary (point of known river channel flow) the river channel flow directly above the subsequent structure (node) is calculated by adding the flow entering the subreach to the product of the calculated subreach gain and subreach length. This calculated flow can also be regarded as the flow exiting the contained subreach's lower boundary. 2. Following the calculation of the river flow directly above a river node, the flow directly below the same node can be determined. The river flow occurring at a point immediately down river of a node is the result of combining the previously calculated river flow directly above the structure with any diversions and/or inflows occurring at the structure. If the node is representative of a diversion point (canal or ditch), the diversion flow is subtracted from the river flow directly above the node. Conversely, if the node represents an inflowing stream the flow directly below the node is computed by adding the flow directly above the node to the inflowing stream. The calculated river flow directly below the structure can be likened to the river flow entering the upper boundary of the subsequent subreach. 3. Once the river flow directly below a structure is determined, steps 1 and 2 can be reiterated in a piecewise fashion down river for all subreaches until the lower reach boundary occurs. As previously defined, the lower reach boundary is denoted by either a gauging station or a diversion structure drying the river. 4. Upon the completion of step 3, all river flows within the upper most reach have been determined. If flows are to be determined for subsequent reaches, steps 1 - 3 are to be repeated until the lower boundary of the river segment of interest is reached. The concluding river flows occurring directly up river and down river of each node are then archived to a table or database (flowout.dbf) by structure name and historical date. Note that river flows occurring above and below a gauging structure are identical in magnitude. There may be instances in which the procedure above results in a negative flow at a point directly below a node. Such an occurrence is directly linked to the assumption that reach gains occur in a uniform manner over the entire reach length and, as discussed above, such assumptions often over - simplify the river 'system'. For instance, if river gains truly occurred at a much higher rate near the upper portion of a designated river reach (underestimated by uniform distribution) and a much lower rate near the lower portion (overestimated by uniform distribution), then flows directly below a diversion structure located near the up river portion of the reach could become negative. Thus, the canal/ditch is diverting more water than was estimated to be flowing directly above that particular diversion structure. A negative river flow value cannot occur and is rectified by designating the affiliated structure as a diversion drying the river. In other terms, the river flow directly below the structure is forced to zero (0). Following re- designation (which results in an E:3 ptflguid.Wpd I 1