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Objects and Methods : Groundwater Storage : User Methods : Groundwater Pumping
Groundwater Pumping
These methods are used to model pumping from a groundwater system. The solution strategy is based on mass balance equations.
* None
This is the default method. It performs no calculations.
There are no slots specific to this method.
* Input Pumping
This method is designed to be used with the conjunctive use methods on the Agg Diversion Site and WaterUser objects. It models groundwater pumping by simply removing a given amount of water from storage. This method is dependent upon the selection of the Single Computed Outflow in the Solution Type category.
Slots Specific to This Method
 Available For Pumping
Type: SeriesSlot
Units: flow
Description: the amount of water that can be pumped from storage
Information: If not input, it is calculated based on the previous timestep’s storage value and the current timestep’s outflow and percolation values. This slot is usually linked to the Available Supplemental Water slot on the Agg Diversion Site
I/O: Optional
 Pumped Flow
Type: Multi Slot
Units: flow
Description: the amount of water removed (per timestep) from groundwater storage
Information: Can be input by the user, but is usually linked to the Supplemental Diversion slot on the Agg Diversion Site or WaterUser.
I/O: Optional
 Water Table Elevation
Type: SeriesSlot
Units: length
Description: elevation of the groundwater table
Information: This slot is only used to hold data for calibration purposes. It is not used in any calculations and is never calculated.
I/O: Optional
Method Details  
If Available For Pumping is not input by the user, it is calculated from the previous timestep’s storage and the current timestep’s outflow and percolation. A local variable, storage flow, is calculated as the previous timestep’s Storage value divided by the length of the current timestep. This represents the flow rate required to drain the groundwater of all its stored water in the current timestep.
Available For Pumping is then calculated as follows:
    
If a GW Deep Percolation method is not selected, Percolation is assumed to be zero.
Pumped Flow should receive its value from a link to Supplemental Diversion on the Agg Diversion Site or Water User. It is then converted to a volumetric value, volume pumped (Pumped Flow multiplied by the timestep length), and used in the mass balance equation (see Dispatch Methods).
* Input Pumped Flow
This method is designed to be used with the conjunctive use methods on the Agg Diversion Site and WaterUser objects. It models groundwater pumping by simply removing a given amount of water from storage. Flow may be input or linked. When linked the water user(s) will determine the pumped flow based on the conjunctive use and supplemental diversion calculations. This method is dependent upon the selection of the Head Based Groundwater Grid in the Solution Type category.
Slots Specific to This Method
 Pumped Flow
Type: Multi Slot
Units: flow
Description: Water removed from the groundwater by pumping (expressed as a flow rate)
Information: Removed from storage via the mass balance equation
I/O: Input or linked
 Available For Pumping
Type: Series Slot
Units: flow
Description: The water available for pumping on a given timestep
Information: If not input, the Available For Pumping is the current storage (before pumping is removed).
I/O: Optional; computed if not input
Method Details  
This method is called from the Solve given Inflow from Surface Water dispatch method.
If Available For Pumping (at t+1) is not input by the user, it will be set as the current, computed storage value converted to a flow rate minus percolation minus ET as a flow. This value will propagate to the linked water user objects which can then dispatch and compute their supplemental diversions. These values return to the groundwater object in the Pumped Flow slot. The groundwater object will then redispatch and recompute storage given the new values for Pumped Flow. The full equation is as follows:
    
Variables in this equation that are not defined (due to the method selection) or are unknown are assumed to be zero. The Available for Pumping value will propagate to the linked water user objects which can then dispatch and compute their Diversion which is passed back to the Groundwater object as Pumped Flow. The current storage will be computed by the mass balance equation described in the Solve given Inflow from Surface Water dispatch method.
Note:  Since the same Available For Pumping value can be referenced by several water users, the water users could pump the groundwater dry if the storage is small and each water user pumps up to the Available for Pumping. There is no mechanism to short water users or prioritize pumping if the demand exceeds the Available For Pumping. Rather, each water user can take up to the available and the groundwater storage will go negative. If this happens, RiverWare issues a warning message but does not terminate the run.
Revised: 12/06/2024