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<br />Network Data <br /> <br />. "l r ::::: ,', <br />. ,. ..., ~ <br />Power .. <br />. . ~ \. <br /> <br />4.3 Power <br />Power plants may only occur at reservoirs. <br />Generated power is given by the formula: <br />E = .0010241 x F x H x Y <br /> <br />where <br /> <br />E = generation, in megawatt-hours <br />F = flow, in acre-feet/month <br />H = head, in feet <br />Y = plant efficiency, as a fraction and H is defined as reservoir surface elevation <br />minus tailwater elevation. <br /> <br />4.3.1 Power reouirement table: Optional. If omitted, the requirement is assumed to <br />be zero. This is a table of monthly values. If non-zero, HYDROSS will treat this as a project flow <br />requirement and draw (if necessary) on stored water in order to generate the required power. <br /> <br />4.3.2 Maximum Dower: Required, Constant. This is the maximum power which can <br />be generated in anyone month. HYDROSS assumes that any discharge from the reservoir will go <br />through the power plant first; if the flow is enough to generate more than this maximum power (using <br />the formula above) then the excess flow is considered not used for generation. HYDROSS will not <br />report generated power above this value. <br /> <br />4.3.3 Water rie:ht date: Optional. If omitted, HYDROSS assumes a value of 9998 <br />(very low priority). In effect, power becomes a project instream flow requirement; the required flow <br />value will depend on the power requirement, the efficiency, and the head. HYDROSS decides for <br />itself what the flow requirement will be. <br /> <br />4.3.4 Tailwater elevation: This value subtracted from the surface elevation of the <br />reservoir (determined from the mean content), gives the head (H in the formula). Tailwater elevation <br />may be expressed as: <br />(1) a constant, or <br />(2) a table of monthly values, or <br />(3) a function of the station flow (below the dam) <br />The last case requires two type-l (parameter/function) tables, and is intended for cases such as <br />Buffalo Bill dam on the Shoshone River in Wyoming, where the channel below the dam is very <br />narrow and the tailwater elevation varies significantly with the flow. <br />4.3.5 Power Dlant efficiencv: The efficiency is expressed as a percentage, and <br />converted to a fraction internally for computations. Efficiency may be expressed as: <br />(1) a constant, or <br />(2) a function of head, or <br />(3) a function of station flow <br />The last two cases each require two type-1 (parameter/function) tables. <br /> <br />March 25, 1991 <br /> <br />HYDROSS 4.1 <br /> <br />Page 25 <br />