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<br />. '0l1UJ3i <br /> <br />The Resident Power and Reservoir ~ystem Model (PRSYM) <br /> <br />capacity at specified project(s) or the minimum elevation level for particular project(s). <br />Simple constraints may, however, also vary with time (e.g., an operating guide which <br />defines a minimum target elevation at any given time for particular project(s)). <br /> <br />Complex constraints may involve groups of projects or be conditional or dynamic. For <br />example, a minimum generation may be required from a group of large tributary projects. <br />Conditional constraints are only activated under certain specified conditions, such as a <br />prescribed reservoir release that is triggered when total system storage drops below a critical <br />level. Dynamic constraints are formulated using model variables that are determined as the <br />model runs. A project release that is a function of upstream releases plus natural inflow is <br />an example of a dynamic constraint. <br /> <br />PRSYM must be capable of handling both linear and non-linear types of constraints. It must <br />be assumed, however, that the constraints can be expressed as differentiable functions. In <br />some circumstances, it may be necessary to model the non-linear constraints iteratively or in <br />a piece-wise linear fashion. <br /> <br />(Finally, the user should have the option to either satisfy the constraints in a prioritized <br />manner or to allow trade-offs among constraints. This implies that there must be <br />mechanisms for prioritizing constraints, resolving conflicts among constrain_ts, or assigning <br />weights to constraints. <br /> <br />If constraints are violated, an option should exist to ensure 'balanced violation.' For <br />example, if it were necessary to violate some minimum elevations in tributary reservoirs to <br />meet some higher priority downstream minimum flow, the model should violate all projects <br />by some small amount rather than lump all of the violation into one or two projects. It must <br />also be possible to express permitted violations either as absolute functions or in terms of a <br />scaling function such as percentage. <br /> <br />Variable Temporal Resolution and Horiwn <br /> <br />The PRSYM model must be capable of operating at variable time steps including daily, <br />weekly, and monthly. The daily time step will be utilized to develop the near term reservoir <br />system schedule, extending from the current status (today) up to a maximum of 14 days. <br />Weekly or monthly resolution will be used for seasonal forecasting (14 days to 6 months) <br />and operational/policy planning (multi-year). The model, therefore, must have the capability <br />of using a graduated time step approach and the system must operate smoothly in the <br />transition from near term to long term. The model user must be able to specify the time <br />step. <br /> <br />Additionally, the user must be able to determine the time horizon by specifying the number <br />of days, weeks, months, or years, as appropriate. The model must be capable of performing <br />discrete, multiple simulations from a specified starting point and for a given time period, as <br />well as continuous, multi-year simulations. <br /> <br />3-9 <br /> <br />""..-.. --- -- - -~-- <br />