Simulation Objects

The following enhancements to the RiverWare simulation objects are described briefly. The user is encouraged to consult the Simulation Objects Documentation in the RiverWare help for more detailed descriptions of the enhancements to the objects and their methods.

Computational Subbasin

Mead Flood Control Method

The Mead Flood Control method has been added to the Computational Subbasin. This method was developed for the CRSS-Lite annual timestep model and cannot be used with other models. The method is used for annual flood control calculations on Lake Mead. A series of CRSS-Lite slots and objects, identified by name and type, must exist on the workspace and be members of the computational subbasin for the subbasin analysis to succeed.

Reservoir Objects

Monthly Evap Calc Annual Timestep Method

A new evaporation method, MonthlyEvapCalcAnnualTimestep, has been added to all reservoir objects. This method calculates evaporation on an annual timestep using monthly coefficients and was developed for use with the CRSS-Lite model. This method is general enough to be used with any annual timestep model that has monthly evaporation coefficients.

Storage Reservoir

Tailwater Calculation Category

The Tailwater Calculation category has been added to the Storage Reservoir. A single method, Input Tailwater Elevation, was added to the category. This method is used if the tailwater elevation is linked to the downstream reservoir pool elevation or directly input by the user. There are no tailwater elevation calculations associated with this method. In other words, the outflow does not affect the tailwater elevation other than by changing the downstream pool elevation. When the tailwater elevation is above the tailwater reference elevation, the effective head is used to compute the max release via the ‘Head Vs Max Release’ table. Otherwise, the max release is calculated using the average Pool Elevation and the Max Release table. The following slots are associated with this method: Tailwater Elevation, Tailwater Reference Elevation, Effective Head, and Head Vs. Max Release.

Slope Power Reservoir

Slope Storage Coefficients Category

A new method category, the Slope Storage Coefficients category, has been added to the Slope Power Reservoir. The category contains two methods: Impulse Response Coefficients and Weighting Coefficients. The Impulse Response Coefficients method is the default and calculates segment and reservoir storage in the previously existing manner. The Weighting Coefficients method uses weighting coefficients to calculate the segment and reservoir storage. When the Weighting Coefficients method is selected, the reservoir can be divided into longitudinal partitions and the steady flow through each partition (intermFlowParams) is calculated. The flow parameter at each partition is then used in a 3-D table interpolation to find the backwater elevation at each of the partitions. This method replaces the Slope Partition Category and Partition BW Elevation method. Existing models that used the Partition BW Elevation method must be updated by selecting the Weighting Coefficients method and reimporting data into the method dependent table slots. The Weighting Coefficients method works with both simulation and optimization.

Inline Power Reservoir

Computation of Hydro Capacity

The Hydro Capacity slot that is used in optimization was previously being computed/linearized as Maximum Turbine Release times the Power Plant Capacity Fraction. This flow value is now converted to power using the Flow Power Table. This is done for both simulation and optimization. Also, because optimization now calculates the Hydro Capacity at the beginning of the run, this removes the need to linearize Hydro Capacity and it is now a SeriesSlot instead of a AggSeriesSlot. Note that Hydro Capacity is now only available and computed if a power method is selected.

Bifurcation Object

Fractionally Split Outflows method

A new method category, Outflow Calculation, has been added to the bifurcation object. This category contains two methods: Two Outflows and Fractionally Split Outflows. The Two Outflows method is the default and solves exactly as the bifurcation did previously. The Fractionally Split Outflows method allows users to split the outflow into multiple outflow destinations (e.g., more than two). The Split Outflows slot is a nocompute multislot in which each subslot represents one outflow from the bifurcation object. The Outflow Fractions Table is used to calculate what fraction of the total outflow is proportioned to each Split Outflows subslot. When the Fractionally Split Outflows method is selected, the inflow must be known for the Bifurcation object to solve. The Fractionally Split Outflows method is not available for use with optimization.

Solve Downstream Only method

A new method, Solve Downstream Only, allows users to specify that the bifurcation object always solves in the downstream direction (i.e., solve for outflow given inflow). This method can be useful in rulebased simulation models where rule priorities can cause the object to dispatch in different directions, potentially causing problems. This method is available from the Bifurcation Solution Direction category. The default method in this category, Solve Upstream or Downstream, allows the object to solve in the previous manner.

Revised: 08/02/2021