Alternative: In HEC-ResSim, a specific configuration of a model, including the network, operational rules, input time series, and computational options. The alternative does not have a specific time period associated with it.
Constituent: A water quality state variable. For example, water temperature, dissolved oxygen or nitrate concentration.
Diffusion: The vertical transport of a water quality constituent in response to a concentration gradient in a reservoir.
Dispersion: The longitudinal transport of a water quality constituent in response to a concentration gradient in a stream reach.
Element: An individual piece of a ResSim network. It may be a reach, reservoir, or junction element.
Entrainment: The process by which a plunging inflow pulls in water from the upper layers of a reservoir as it travels longitudinally along the submerged bed of a reservoir.
Network: A schematic representation of a river-reservoir system in HEC-ResSim, including reservoir, reach, and junction elements.
Parameter: A coefficient used to configure biogeochemical processes and rates in the water quality transformation libraries.
Region: A subset of a water quality geometry in which a unique set of water quality parameters can be defined.
Simulation: A realization of an Alternative in ResSim, for a specific time period.
Transformation: Water quality reactions, sources, and sinks (for example, heat fluxes or nutrient uptake by algae), as separate from water quality transport.
Transport: The movement of water quality constituents by advection and diffusion, as separate from water quality transformations.
Water quality control device: A ResSim network representation of a physical device on a reservoir outlet used to operate releases to meet water quality objective.
Water quality geometry: The discretized subset of a ResSim network used for water quality modeling. River reaches are discretized as 1D longitudinal sections, and reservoirs are discretized as 1D vertical stacks of layers.
Water quality objective: An at-site or downstream threshold for a water quality constituent, which the reservoir releases are managed to try to meet. For example, maximum water temperature requirement at a location downstream of a reservoir.
Water quality subdomain: An piece of the water quality geometry, for a specific river reach or reservoir.