A geometry dataset is essential for all water quality models, as it defines the water quality domain, computation elements, river-reservoir network connectivity, and water body discretization information. The geographic extent of the geometry dataset is determined by the selected ResSim network, and it can be subdivided into regions for grouping watershed elements. Water quality regions are used to define spatially varying water quality parameters and meteorological stations within the model domain.
The geometry dataset is created using the ResSim reservoir network, a HEC-RAS geometry shapefile, and a steady flow file (refer to Create a New Geometry for detailed instructions on creating and defining the geometry dataset). The HEC-RAS geometry shapefile is used to define water quality cells for river reaches. By default, these cells are predefined using hydraulic cross-sections. Each water quality cell has two faces corresponding to hydraulic cross-sections. The default configuration of water quality cells can be adjusted as necessary, as outlined in Edit River Reach Water Quality Cell Length. For water temperature modeling, the geometry dataset is linked to a meteorological dataset (refer to Chapter 3). This dataset is used by the geometry dataset (refer to Geometry Editor – Met Stations Tab) to assign each water quality region to a specific meteorological station within the linked dataset. When connected to a meteorological dataset, each water quality region (defined within the geometry dataset) is individually assigned to a particular meteorological station.
The prerequisites for creating a water quality geometry dataset include the ResSim reservoir network, HEC-RAS geometry file, HEC-RAS steady flow file, and Meteorological Dataset. Note that this manual serves as a supplement to the HEC-ResSim User's Manual, and users should refer to HEC-ResSim Version 4.0 for general software information. For detailed guidance on the HEC-RAS geometry and steady flow model, refer to the HEC-RAS User's Manual.
Additionally, the geometry dataset is required when creating the following datasets: WQ Parameters Dataset (Chapter 6), Initial Conditions Dataset (Chapter 9), Boundary Conditions Dataset (Chapter 8), Mixing Coefficient Dataset (Chapter 10), and Mass Injection Dataset (Chapter 11).