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<br />-. <br /> <br />Simulation Model Operation <br /> <br />At the beginning of a run reservoir operational data, initial de.. <br />mand data, and the firet year of hydrology inputs are read in. The one <br />year of hydrology data is placed in a temporary file. This temporary <br />file is then ac,cessed during the streamflow,forecast procedure and each <br />month for new hydrology data. <br />The model simulates river basin flows on a monthly time frame <br />starting at the top of the basin and proceeding completely through the <br />basin to the bottom. Simulation is don~ node by node in the order <br />specified in the node control structure input. Within a node, computaw <br />tione are. made from the upstream to downstream end. The general <br />operation of the simulation model is shown schematically on Figure 4. <br />RiverIlow8 are calculated at each inflow, demand, and reservoir <br />aequence point. All calculations for river flow are based on the con- <br />tinuity equation: <br />Flow at next sequence point =- Flow from preceding sequence point <br />... Inflow - Demand <br /> <br />When there is not enough flow in the river at a sequence point to <br />supply a demand, a search is made of upstream reservoirs for the <br />additional water needed. II there are upstream reservoirs and they have <br />sufficient water in storage to meet the demand, the additional increment <br />needed is released and routed through the sys.tem to the point in need. <br />If adequate water is found, the demand is ~et and the calculations pro-" <br />ceed to the next point downstream. If this second demand cannot be met, <br />the amount of shortage is computed and printed and calculations proceed. <br />All calculations ,for reservoir operatlons are based on another <br />form of the continuity equation: <br />Change in storage = Inflow - Outflow - Evaporation - Bank storage <br />A re servoir is operated to mect a target end-ai-month conlents. <br />A 'releasc is determined by either a minimum release rate, a flood <br />apace storage requirement, dem~nds which draw from the reservoir, <br /> <br />150 <br /> <br />.. <br /> <br />. <br /> <br /> <br /> <br />L6tl <br /> <br />READ <br />INITIAL <br />INPUT <br /> <br />UPDATE INPUT <br /> <br />NO <br /> <br />YES <br /> <br />Figure 4. OperaUonal ac:.hematic of river basin simulatioD model. <br /> <br />151 <br />