The Reservoir Network module operates the same way for water quality-enabled watersheds as it does for regular HEC-ResSim watersheds. For detailed information about this module, as well as other general HEC-ResSim software guidance, users should refer to the HEC-ResSim Version 4.0 User's Manual. The water quality model is built upon an existing ResSim reservoir network. However, certain reservoir properties, such as surface area and outlet geometry, may not be available in the standard ResSim flow model. As a result, it is essential to include this information for the reservoirs. Furthermore, updating or modifying the existing reservoir network might be required to perform a water quality simulation. This process may involve removing certain reservoirs, river reaches, and their associated connectivity, followed by reinserting them into the network. These changes should be carefully executed within the Reservoir Network module.
It is important to note that modifying reservoir network elements can lead to the loss of essential data such as reservoir physical properties, operation sets, connectivity, time series data, and more. If updating the reservoir network is necessary, users should follow the procedure outlined in the HEC-ResSim User's Manual.
For each reservoir included in the water quality model domain, it is necessary to define a pool Elevation-Storage-Area curve as illustrated in the table below. While the surface area column is not required for the ResSim flow model, it plays a critical role in water quality simulations. If the required reservoir surface area data is unavailable, it can be obtained from the CE-QUAL-W2 model and incorporated into this table.
Reservoir pool Elevation-Storage-Area Table
The outlet geometry of reservoirs, including those with power plants and spillways, must also be defined for the water quality model. This includes specifying the outlet shape, which can be either Rectangular or Circular, as well as the outlet invert elevation. Additionally, it is necessary to indicate whether the outlet gate opens from the Top, Bottom, or Center. All outlet geometry details must be provided in the Reservoir Network module before creating a water quality geometry. However, if needed, this information can be updated using the Update From Network button located in the lower left corner of the Geometry Editor (Geometry Editor- Update From Network... button). Clicking this button will update the water quality geometry to reflect any changes made to the reservoir outlets and water quality control devices.
Geometry Editor- Update From Network... button
To manage downstream water quality for a reservoir, users can optionally define a water quality control device, which may be assigned to a single outlet or an outlet group within reservoir operations. For detailed instructions on defining water quality reservoir operation rules, refer to Chapter 12.
To perform a water quality simulation in ResSim, any required changes to reservoirs, river reaches, and computation points within the network must be made in the Reservoir Network module. These updates will not automatically transfer to the existing water quality geometry once a water quality geometry dataset is created. In other words, updating the reservoir network does not automatically update the water quality geometry in ResSim. Therefore, it is recommended to complete all necessary updates to the reservoir network elements prior to developing the ResSim water quality model.