Seepage

The Seepage methods are used to calculate the amount of water lost through the face of the dam. The volume of seepage computed during the execution of these methods affects the mass balance of the Reservoir.

None

None is the default for the Seepage category. It is used when the user does not want to calculate the flow of water through the face of the dam.

Input Seepage

The Input Seepage method is used when it is desired to have the seepage slot as input or set by a rule.

Slots Specific to This Method

Seepage

Type: SeriesSlot

Units: FLOW

Description: Flow of water through the dam face

Information: Seepage is not included in the Outflow of the reservoir and will need to be linked separately if the water does in fact go downstream.

I/O: Input only

Links: Linkable

Linear Seepage

The Linear Seepage method calculates the seepage from the face of the dam. This calculation is based on the Pool Elevation of the Reservoir and specified coefficients.

Slots Specific to This Method

Seepage

Type: SeriesSlot

Units: FLOW

Description: Flow of water through the dam face

Information: Seepage is not included in the Outflow of the reservoir and will need to be linked separately if the water does in fact go downstream.

I/O: Output only

Links: Linkable

Seepage Coefficients

Type: TableSlot

Units: LENGTH, AREA per TIME, FLOW

Description: Coefficients in the linear equation for seepage

Information: The first coefficient (column zero) is the base elevation of the dam. The second coefficient is the slope of the linear equation for seepage. The third coefficient is the intercept of the linear equation for seepage.

I/O: Required input

Links: NA

Method Details

The calculation for Seepage in this method is fairly straightforward. A linear model is used. The coefficient are user inputs. The following equation is used to compute Seepage:

Single Seepage Value

The Single Seepage Value method sets the seepage from the face of the dam equal to a scalar value.

Slots Specific to This Method

Seepage

Type: Series

Units: Flow

Description: Flow of water through the dam face

Information: Seepage is not included in the Outflow of the reservoir and will need to be linked separately if the water does in fact go downstream.

I/O: Optional Input

Links: Linkable

Single Seepage Value

Type: Scalar

Units: Flow

Description: seepage value to be applied to each timestep

Information:

I/O: Required input

Links: Not linkable

Method Details

This method is executed at the beginning of the run. For each timestep from the initial timestep through the end of the run (plus post run dispatching timesteps too), if the Seepage is not input, the Seepage is set equal to the Single Seepage Value.

The method will issue an error if there is not a valid value in the Single Seepage Value slot.

Note: This structure allows some flexibility. Seepage can be input/rules when necessary but will use the scalar value when not input.

Linked Seepage

This method is intended to be used when linking a Reservoir object with a Groundwater Storage object that uses the Head Based Boundary Condition method in the Solution Type category. See Head Based Boundary Condition for details.

Slots Specific to This Method

Seepage

Type: Series

Units: Flow

Description: Flow of water out of the reservoir, often into groundwater

Information: A positive value is flow out of the reservoir.

I/O: Output only if linked to a Groundwater object (typical); otherwise required input

Links: Must be linked, typically to Inflow from Surface Water on Groundwater object

Previous Pool Elevation

Type: Series

Units: Length

Description: Pool Elevation at the end of the previous timestep

Information:

I/O: Output only

Links: Typically linked to the Elevation Previous slot on a Groundwater object

Method Details

This method does not do any calculations; it just adds the appropriate slots. The Reservoir does provide the Previous Pool Elevation which is then linked to the Groundwater object Elevation Previous. The Groundwater object computes the Inflow from Surface Water, which is linked back to the Seepage slot on the reservoir. The Seepage is used in the Reservoir mass balance.

Figure 29.2

See Head Based Boundary Condition for details on how Seepage is calculated as Inflow from Surface Water on the linked Groundwater object.

Revised: 08/02/2021