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<br />002025 <br /> <br />Network Data <br /> <br />Reservoirs <br /> <br />4.2 Reservoirs <br />4.2.1 Area-Content tables: Each reservoir must have each of four type-I <br />(parameter/function) tables which relate the content to: <br />(I) Surface elevation, used to determine head for power plants. <br />(2) Surface area, used to determine evaporation losses. <br />(3) Maximum discharge, used to model spills. HYDROSS tries to route all releases <br />through the outlet worlcs; releases which won't fit through the outlet worlcs are spills. <br /> <br />HYDROSS uses the mean reservoir content (average of beginning-{)f- month and <br />end-{)f-month contents) and perfonns linear interpolation on the tables to determine the elevation, area <br />and maximum discharge for the month. <br /> <br />4.2.2 Content at soillwav level: Constant. At or below this level, the reservoir <br />cannot spill water and releases are restricted by the outlet worlcs capacity (maximum discharge). <br /> <br />4.2.3 Evaooration table: Optional. This is a monthly table of (linear) values which <br />give the depth of evaporation per unit of surface area. Multiply by the surface area to get the water <br />volume lost to evaporation in a month. If omitted, evaporation will be zero. <br /> <br />4.2.4 Maximum content table: Optional. This table gives the maximum allowable <br />content in the reservoir each month. If omitted, HYDROSS uses the last (highest) value in the AC <br />content table (see above). HYDROSS will try to release (either discharge or spill) any water above . <br />this level. However, the release may be blocked by a channel capacity constraint downstream or by <br />the outlet worlcs capacity if the level is below the spillway elevation. <br /> <br />4.2.5 Minimum content table: Optional. This table gives the minimum allowable <br />content in the reservoir each month. If omitted, HYDROSS uses the first (smallest) value in the AC <br />content table (see above). HYDROSS will not release water below this level for any reason; the only <br />losses will be seepage (see below) and evaporation. <br /> <br />4.2.6 Tar!!et content table: Optional. This table gives the desired content in the <br />reservoir each month. If omitted, HYDROSS uses the maximum content (see above). The target <br />content is used for pool maintenance and for determining diversion demands for offstream storage. <br /> <br />4.2.7 Share flair: Optional, defaults to 0 (share mode) ijamitted. The pool <br />maintenance routine attempts to balance reservoir contents around the target levels by releasing water <br />from upstream reservoirs to downstream reservoirs. Normally, this is the way you will want to have <br />it. Occasionally, as with offstream (pumped) storage, you will want to disconnect a reservoir so that <br />it will not contribute to the maintenance of downstream reservoir pools. Set the share flag to I (no- <br />share mode) to prevent a reservoir from contributing to downstream maintenance. <br /> <br />4.2.8 Seeoa!!e: Optional. Seepage!s an uncontrollable release from the reservoir that <br />does not use any of the outlet worlcs capacity, and always appears immediately below the reservoir as <br />project flow. Seepage may be given as: <br />(I) a constant, or <br />(2) a table of monthly values, or <br />(3) a function of surface elevation, or <br />(4) a function of reservoir content <br />The last two cases require two type-l (parameter/function) tables. HYDROSS uses the <br />parameter value (elevation or content) and perfonns linear interpolation on the tables to <br />determine the seepage flow. <br /> <br />HYDROSS 4.1 <br /> <br />March 25, 1991 <br /> <br />Page 24 <br />