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<br />Ou20!9 <br /> <br />Advanced Concepts <br /> <br />Reservoir Levels <br /> <br />5.3 Reservoir Levels <br />HYDROSS uses 5 levels in the reservoirs. The uses of each level are described in this <br />section. The levels are: <br />Absolute maximum - Defined as the last (highest) entry in the AIC content table. <br />Conceptually, this is the top of the dam. Contents above this level will be <br />discharged or spilled without regard to downstream channel capacity (or flood <br />damage). <br />Maximum - Defmed by a table (possibly staged). The model will not willingly retain <br />water in the reservoir above this level,and will try to discharge or spill.the <br />excess (constrained by downstream channel capacity). <br />If you omit the table definition, the model defaults to the absolute maximum. <br />Target - Defined by a table (possibly staged). This level has only two uses, and is <br />otherwise ignored. One use is in offstream storage (to determine the diversion <br />demand as the difference between target content and actual content), the other <br />use is in pool maintenance (See next section). <br />If you omit the table definition, the model defaults to the maximum. <br />Minimum - Defined by a table <P.ossibly staged). At or below this level, the model <br />will not discharge water from the reservoir. The only losses will be from <br />seepage andlor evaporation. <br />If you omit the table definition, the model defaults to the absolute minimum. <br />Absolute minimum - Defined as the first (lowest) entry in the AIC content table. <br />Used only as a default, in case you omitted the table definition for Minimum <br />above. <br /> <br />5.4 Precipitation on Reservoir Surface: <br />Reservoir evaporation is subtracted from the volume of water stored in a reservoir. <br />HYDROSS assumes that all water stored in a reservoir is project water. Thus, evaporation leaves the <br />reservoir as project water. <br />If the reservoir has a negative evaporation (precipitation exceeds evaI') for a given month, the <br />volume of water resulting from the negative evaporation is added, as project flow, to the volume of <br />water stored in the reservoir. <br />If the reservoir is full at the time of precipitation, the excess volume of water resulting from <br />precipitation on the reservoir surface is released from the reservoir as project flow. In actuality, this <br />water should be released as natural flow. <br />Evaporation should never be negative, since the pristine station gain is assumed to be include <br />all natural inflow. However, the model does not declare negative evaporation as an error, and you <br />may use this feature if you need the special effects. <br /> <br />Page 32 <br /> <br />HYDROSS 4.1 <br /> <br />March 25, 1991 <br />