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The solver’s purpose is to determine prioritized water allocations according to the doctrine of Prior Appropriation. In particular, the solver meets the following requirements:
• Three distinct types of water rights can be represented in RiverWare by legal accounts, and can receive priority allocations:
– The right to divert from a stream, represented in RiverWare by a Diversion Account.
– The right to store water in a reservoir, represented in RiverWare by a Storage Account.
– The right to minimum in-stream flow, represented in RiverWare by an Instream Flow Account.
• Water rights (legal accounts) that receive priority allocation have a unique priority date; that is,, no two water rights may have the same priority date.
• A right’s allowed quantity of water may be described in various ways on legal documents or in practice; the model capabilities must be flexible enough to represent these, and to be extensible to add representations later that are not initially provided.
• Allocation to a junior right may not short the available water to a senior right.
• Some rights are subject to physical constraints such as the physical capacity of a diversion structure or the size of a reservoir pool.
• Some rights are subject to legal constraints such as accrual-based maximums. Some legal constraints are defined in terms of the state of the network after senior rights have been satisfied, such as minimum bypass requirements that are expressed as a function of the flow in the river.
• The effects of an upstream allocation on a downstream senior right must take into account lags and losses as water moves downstream.
• The solver is intended to allocate only Allocatable Flow. Hence, it does not solve for any diversions from storage accounts, or releases from storage accounts to meet downstream needs. Such allocations are expected to be addressed with other rules and are not priority-date driven.
• The solver can be executed more than once during a timestep, with different sets of instream flows being allowed to call water from junior upstream rights.
Revised: 08/02/2021