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Water Quality Input Types
Water quality model inputs consist of the following: model geometry, water quality constituents, water quality parameters, meteorological data, water quality boundary conditions for all inflow, initial conditions for simulated constituents, mass injections, dispersion coefficients, and observed water quality concentration data for the model calibration and validation. The table below provides a description of each of these required or optional water quality (WQ) data. Water quality stations include Met stations and water quality monitoring stations in this manual. They provide observed water quality and meteorological time series data for the water quality model.
Input Data | Description |
Geometry | This required input for all water quality models represents the water quality (WQ) domain, which includes river-reservoir network connectivity and discretization information. The geographic extent of the geometry data set can be subdivided into regions, which are used to group watershed elements that share water quality parameters. Further, the geometry dataset is based on an HEC-ResSim network and an HEC-RAS geometry shapefile and steady flow model output file. For temperature modeling, the geometry data set is also linked to meteorological data. |
WQ Constituents | These are the water quality variables to be simulated (e.g., water temperature, dissolved oxygen, nutrients, etc.) and required inputs for all water quality models. Users select water quality variables from the list of constituent water quality Libraries (DLLS). Each Library contains different constituents (see Appendix B for a full list of available constituents by library). Users may also add global reference values. |
WQ Parameters | These are the coefficients used in the calculation of constituent transformation and are required for all water quality models. Water quality parameter sets are created from geometry and water constituent datasets. When the linked geometry data set contains regions, users can enter separate coefficients and constants by region or for the entire geographic extent. |
Meteorological Data | This data is optional for water quality modeling; however, meteorological data is required for temperature modeling. The meteorological dataset includes atmospheric pressure, air temperature, humidity, shortwave radiation, cloudiness, and wind speed. |
Observed WQ Data | This data includes observed water quality concentration information for model calibration and/or validation and is not required to run an HEC-ResSim water quality model. |
Boundary Conditions | This input represents the water quality boundary concentrations for inflows and is required for all water quality models. |
Initial Conditions | This input represents the water quality initial concentrations at the start of the simulation and is required for all water quality models. |
Mass Injections | This data represents any point/non-point source of constituents in the watershed and is optional for water quality modeling. |
Dispersion Coefficients | These required coefficients are the parameters describing longitudinal or vertical mixing rate. |
Units of Measure
In HEC-ResSim, water quality measurement units for input data will function differently than for non-water quality modeling data. In a HEC-ResSim watershed in which water quality is disabled, units of measure are set at the time the watershed is created (see HEC-ResSim User's Manual, Chapter 3, Section 3.3), and all modeling data (time-series data, geometric and reservoir information, model parameters, and flow-, elevation-, and stage-time-series data) must use the same unit system when saved.
In contrast, units of measure are more restricted in a water quality watershed. In many cases, water quality input data can be imported in a variety of units (selected from dropdown menus); further, these menus are not contingent on the units of measure set for the watershed but instead are specific to the water quality libraries used at compute time. However, there are situations where the units listed in a water quality editor are contingent on the watershed units of measure and watershed display units (see HEC-ResSim User's Manual, Chapter 1, Section 1.1). For example, Relative Elevation (refer to Section 2.2.3 of this manual) displays either feet (ft) or meters (m), depending on the set watershed units of measure and the watershed display units.