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<br />Ou~3Z8 . <br />The Resident Power and Reservoir System Model (PRSYM) <br /> <br />Evaporation <br /> <br />The PRSYM simulation module must include the capability to compute reservoir and <br />river reach evaporation when that process is deemed important. Evaporative losses <br />should be included in the mass balance computation. Simplified methodologies, such <br />as the application of predetermined coefficients to the surface area, can be used. <br /> <br />\ <br /> <br />Reservoir Release <br /> <br />L' 1 <br /> <br />PRSYM must have the capability to compute total reservoir release in terms of <br />turbine discharge and spill. Maximum and actual discharge released through the <br />turbines and/or spilled must be calculated as a function of net head, which depends on <br />headwater and tailwater elevation. <br /> <br />, <br />~, <br /> <br />f <br /> <br />,/ <br />;;': <br />" <br /> <br />It must be possible to either specify the reservoir release at each time step (i.e., solve <br />for generation and storage) or to solve for release, in which case the model output <br />would include the release schedule. In either case, the model must verify at each <br />time step that the maximum and minimum release values have not been violated. The <br />minimum release may be a simple quantity, a time series, or a function of other <br />model parameters. The maximum discharge (sum of the maximum turbine discharge <br />and spill) is, in general, a function of effective head and maximum turbine capacity. <br /> <br />At many reservoirs, the effective head is a function not only of headwater elevation, <br />but also of tailwater elevation. The tailwater elevation may, in turn, be a function of <br />total release. Thus the solution must be iterative or by some method converge on a <br />solution which satisfies the head-release-tailwater dependencies. <br /> <br />The maximum turbine discharge can be either the best-efficiency discharge or the full <br />gate discharge. PRSYM should support the specification of either of these options. <br />In both cases, the functional relationship between maximum turbine discharge and <br />effective head (i.e., unit characteristics) must be available to the model as data. (This <br />data should be verifiable by the user to ensure that it reflects projected turbine status <br />and maintenance schedules.) Functional relationships between spill and head must <br />also be provided as data. <br /> <br />When. utilizing a daily time step, it should also be possible to account for differences <br />in reservoir releases due to varying hydropower demands on weekdays vs weekends. <br /> <br />Hvdrooower Generation <br /> <br />Once the release has been determined, the model should be able to compute <br />hydropower generation based on the release, effective head, and unit characteristics. <br />If no spill is involved and the total plant release is less than the maximum (full gate) <br />discharge, then the most efficient combination of units must be identified to determine <br /> <br />3-6 <br /> <br />~-- <br />