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<br />OO~022 <br /> <br />Basic Concepts <br /> <br />Inflow <br /> <br />3.4.5 Other Gain: 'Other gain' is a means of forcing project water into the system <br />outside of normal channels (Le. by magic). It is potentially useful for introducing regulated (project) <br />flows from a source outside the scope of the model, such as releases from a reservoir controlled by <br />another agency. <br />Other gain is achieved by specifying an .other loss. table (col. 23-26 on the ST A card) with <br />negative values (positive table values are a loss, negative values are a gain). <br />Other gain enters the system as project water. <br />Other gain is not quite the project analog of local flow, since it enters the system in addition <br />to (instead of replacing) incremental runoff. This may be an important difference, depending on the <br />requirements of your model. <br />In a given month, a station may have other gain or other loss, but not both. An other loss <br />table record may specify gain for some months, loss for other months, or zero. <br /> <br />3.4.6 Inflow: The inflow to a station is sum of runoff (or local flow), upstream <br />flows, return flows, and other gain. In some cases (the James River in South Dakota), the river may <br />be so sluggish that the station gain is actually a loss greater than can be made up by the other <br />components. In this case the reported inflow will be negative. This does not mean the water is <br />flowing upstream; it represents a deficit and tells you this much water will have to be added at the top <br />of the reach in order to bring the inflow to zero (damp stream bed). <br /> <br />3.5 Station Action <br />Once the inflow reaches the station then all, some, or none of the following things can <br />happen: <br />Other loss <br />Diversions <br />Evaporation (reservoir stations only) <br />Content change (reservoir stations only) <br />Net station action is the sum of the items. The station flow (flow at the station) will be the <br />inflow minus the net station action. <br /> <br />3.5.1 Other Loss: Other loss is achieved by specifying an other loss table (coI23-26 <br />on the ST A card) with positive values. If no such table is specified, there will be no such loss. <br />Other loss is the first thing that happens to the water when it reaches the top of the station, <br />and comes before any diversions. In away, it is a kind of specialized diversion: it will take any kind <br />of water (natural or project) it can get, and deny it to all users at or below this station without <br />reference to priority. If the other loss exceeds the station inflow, the station flow will become <br />negative before any diversions are considered. <br /> <br />3.5.2 Diversions: Water which gets past the .other loss. may be subject to diversion. <br />At this point, the watei: reaching the diversion is the most that could possibly be diverted; the <br />diversion must look downstream to see if any other demand of a higher priority needs the water and, <br />if so, must leave enough water in the stream to satisfy the downstream demand. <br />If the station has a reservoir, the diversion is considered to come from the reservoir itself. <br />Diverted water does not pass through the outlet works of the reservoir, and is not available for power <br />generation. <br /> <br />HYDROSS 4.1 <br /> <br />March 25, 1991 <br /> <br />Page 18 <br />