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Reservoir

Overview

Reservoirs are open bodies of water that store flow and are connected to nodes by means of an energy-based equation. Reservoirs are considered instantly well-mixed.

  • The Reservoirs Table specifies the identity and physical properties of the reservoir.
  • Connections to nodes are specified in the Reservoir Connections table.
  • Reservoir area as a function of elevation is specified in the Reservoir Volume table, while volume is calculated in code (since 8.2).

RESERVOIR Table

Example

# Description:
# Setting of Clifton Court Forebay
RESERVOIR
NAME AREA BOT_ELEV
clifton_court 91.868000 -7.748
END

The RESERVOIR table defines the name and physical properties of the reservoir. In the case of a "tank"-like reservoir, the area and volume are simply defined by the constant area and bottom elevation times the constant area, respectively.

Field Descriptions

  • NAME: Name of the reservoir. This is the identifier of the reservoir used in other tables.
  • AREA: Surface area (in units of million sq ft) of the reservoir at typical depth. This area is used to calculate volume changes.
  • BOT_ELEV: Elevation (ft) of the bottom of the reservoir.

Table Info

  • Identifier: NAME
  • Include Block: GRID

RESERVOIR_CONNECTION Table

Example

# Description:
# Setting of Frank Tract Connections
RESERVOIR_CONNECTION

RES_NAME NODE COEF_IN COEF_OUT
franks_tract 103 2250.000 2250.000
franks_tract 216 1500.000 1500.000
END

The RESERVOIR_CONNECTION table lists reservoir connections to neighboring nodes. Flow through reservoir connections is calculated using the following formula:

Q = Cto sqrt[ 2g(znode - zres) ] ... zres \< znode

Q = Cfrom sqrt[ 2g(zres - znode) ] ... zres > znode

Where:

  • Cto and Cfrom are coefficients representing the hydraulic efficiency of the reservoir connection and the nominal area perpendicular to flow.
  • g is gravity.
  • zres and znode are the water surface elevations at the reservoir and node (node surface is assessed by means of a reference channel that has no reservoirs attached to it).

Field Descriptions

  • RES_NAME: Name of the reservoir at which the connection is specified.
  • NODE: Number identifying the node at which the connection is specified.
  • COEF_IN: Coefficient from node to reservoir, greater than zero. If you compare the reservoir equation to the gate or other orifice equation, you will find that the reservoir coefficient actually folds several quantities into one parameter: a flow efficiency (between zero and one) and an area of flow. If you have an observation of the area normal to flow, the coefficient should be some fraction of this aperture.
  • COEF_OUT: Flow direction out of the reservoir.

Table Info

  • Identifier: RES_NAME, NODE
  • Parent Table: RESERVOIR
  • Parent Identifier: RES_NAME
  • Include Block: GRID

A node may not have more than three reservoir connections and must have at least one ungated channel connection.

RESERVOIR_VOL Table

Example

RESERVOIR_VOL
RES_NAME ELEV AREA
liberty -61.975 0.000
liberty -32.808 2.478
liberty -16.404 16.220
liberty -3.281 272.328
liberty -1.640 1017.270
liberty 0.000 1999.522
liberty 1.640 3031.999
liberty 3.281 4209.851
liberty 4.921 4584.028
liberty 6.562 5190.456
liberty 8.202 6359.679
liberty 9.843 6636.050
liberty 13.123 6731.118
liberty 16.404 6830.894
liberty 19.685 6876.916
liberty 22.966 6890.138
END

Since version 8.2, reservoirs can also have variable area and volume defined as a function of elevation. This table still requires the reservoir to be defined in the RESERVOIR table even though the elevation area specified in the RESERVOIR table will be ignored if it is specified here.

Field Descriptions

  • RES_NAME: Name of the reservoir. This is the identifier of the reservoir and should have been specified in the RESERVOIR table.
  • ELEV: Elevation (ft) of the reservoir at which the area and volume are specified. This elevation is to the datum of the rest of the model (currently NAVD88).
  • AREA: Surface area (in acres) of the reservoir at the specified elevation. The area is interpolated between elevations based on the current elevation of the water level.

Table Info

  • Identifier: NAME
  • Include Block: GRID