Sediment
The Sediment category is used to enable algorithms which adjust reservoir Elevation Volume and possibly Elevation Area relationships in response to sediment inflow.
NoneThe None method is the default for the Sediment category. No calculations are performed in this method.
There are no slots specific to this method.
CRSS SedimentThe CRSS Sediment method is designed based on sedimentation calculations performed by the US Bureau of Reclamation’s Colorado River Simulation System (CRSS) model. This function distributes reservoir sediment based on the Empirical Area Reduction Method. Simply put, sediment is distributed through an iterative process in which a total volume loss due to sedimentation is calculated based on an assumed top of sediment elevation.
Slots Specific to This Method
Elevation Area Table
Type: Table
Units: LENGTH vs. AREA
Description: Generated elevation area table for calculating sediment distribution
Information:
I/O: Output only
Links: Not linkable
Elevation Vol Area Table Increment
Type: Table
Units: LENGTH
Description: Elevation increments for the generated Elevation Volume and Elevation Area Tables
Information: This table often needs more precise elevation increments than the sediment calculation tables.
I/O: Required input
Links: Not linkable
Initial Elevation Area Table
Type: Table
Units: LENGTH vs. AREA
Description: Initial elevation area table
Information: Provided for comparison with initial data
I/O: Output only
Links: Not linkable
Initial Elevation Volume Table
Type: Table
Units: LENGTH vs. VOLUME
Description: Initial elevation volume table
Information: Provided for comparison with initial data
I/O: Output only
Links: Not linkable
Sediment Distribution Coefficients
Type: Table
Units: NOUNITS
Description: Parameters for empirical equation governing sediment distribution
Information:
I/O: Required input
Links: Not linkable
Sediment Inflow
Type: SeriesSlot
Units: VOLUME
Description: Volume of sediment flowing into the reservoir at each timestep
Information:
I/O: Required input
Links: Not linkable
User Input Elev Area Data
Type: Table
Units: LENGTH vs. AREA
Description: Initial Elevation Area relationship
Information: These values are initial conditions for the first timestep of the simulation. The elevation increments will be used for all sedimentation calculations.
I/O: Required input
Links: Not linkable
Method Details
This volume loss is recalculated (with a new top of sediment elevation) at each iteration, until the calculated volume loss is equal to the actual volume of sediment inflow (within a specified convergence). The total volume loss calculation consists of a somewhat complicated algorithm utilizing elevation/area and elevation/volume data for the reservoir and an empirical equation. The empirical equation uses user specified parameters which relate the portion of total area that is taken up by sediment to the Pool Elevation. The empirical equation basically gives the shape of the accumulated sediment. The empirical equation has a close relationship to the elevation volume and elevation area characteristics of a given reservoir. The elevation/area and elevation/volume data is stored in a polynomial coefficient table, which gets recalculated after each timestep. The actual Elevation Area, Elevation Volume tables used by RiverWare are adjusted at the end of the sedimentation code (but prior to the hydrologic simulation).
Caution: Take care when creating input data for this method. The close relationship between the empirical area reduction equation and the shape of the reservoir (reflected in the User Input Elev Area Data) makes the method fairly sensitive to input data. When choosing empirical parameters for this method, physical characteristics of the given reservoir need to be considered. The Bureau of Reclamation currently considers 4 possible types of reservoirs, with each type having a corresponding set of empirical area reduction parameters. The reservoir type classification is based on the shape of the Reservoir, the manner in which the reservoir is to be operated, and the size of the sediment particles to be deposited in the reservoir. The main emphasis is on the shape. Tables are used to classify the reservoirs based on these characteristics. Once the type has been established, the parameter values for that type can also be taken from tables in the literature. An incorrect set of parameters for a given reservoir will lead to an inability to achieve convergence on the sediment distribution within this method.
Revised: 07/17/2020