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Show Final Report Hydrologic Model Analysis of the Provo River Basin 1.3.2 Description of the Model The computer model developed within this study is a prioritized water balance allocation calculator. As shown on the conceptual diagram of Figure 1- 2, PROSIM uses a database including information on hydrology, water rights, facilities, and water requirements. The model produces simulated output describing the flows, deliveries, consumptive use, and reservoir storages that would result given the data and assumptions used in simulating the scenario. The model divides the Provo River system into stream reaches and model nodes shown on Figure 1- 1. A more detailed process schematic is shown in Figure 1- 3 to aid in describing the model operation. For simplicity, diversions, conveyance paths, reservoirs, and return flows are typically numbered to reference the reach and node where they are located. For each timestep, PROSIM calculations start with the virgin or natural flow of the river at each node and each diversion point. Modeled processes are simulated in priority order, with the priority being assigned by the model user or based upon basin rank, interpretations of water rights laws, historical practice, or water user desires. As each prioritized process is simulated, three water balance accounts ( physical, available, and bypass); are updated at each node in the system. Each of these accounts is added to or deducted from, based on the modeled processes ( listed below in 1.3.3). The physical quantity of water represents the actual volume of " wet" water flowing past a given node. The available quantity of water represents the volume of natural water which has not been allocated to a specific user or instream requirement. The quantity of water being bypassed represents a volume of " wet" water that is required to go past the node because of its allocation to a downstream, higher priority use. Reservoir account balances are similarly updated when the specific process being modeled involves a change in reservoir volume or ownership. Reservoirs are subdivided into one or more reservoir owners, which may be further subdivided into one or more reservoir users. This user and owner accounting allows water to be diverted to storage by a single owner under a single water right or rule. Subsequently the stored water is allocated into individual reservoir user's accounts, from which the corresponding water users call water when needed. Alternatively, the reservoir could be set up in PROSIM to allow all water users to draw from a common owner pool. Depending upon the rules under which the reservoir operates, a user's storage balance is either carried over to the following year ( as in the case of Deer Creek Reservoir) or reverted to the owner for reallocation among its users ( as in the case of Jordanelle Reservoir). Water user diversions and remaining demand are also updated at each timestep, when the process involves diversion of water to a user. A water user may have multiple direct flow water rights, multiple exchange agreements for water January 1998 Page 5 |