A groundwater node's (GW) storage in the first month (m) of the simulation is specified as data (see Supply and Resources\Groundwater\Initial Storage).
BeginMonthStorageGW,m = InitialStorageGW for m = 1
Thereafter, it begins each month with the storage from the end of the previous month.
BeginMonthStorageGW,m = EndMonthStorageGW,m-1 for m > 1
The storage at the end of the month equals the storage at the beginning plus inflows from natural recharge (entered as data: Supply and Resources\Groundwater\Natural Recharge), demand site (DS) and treatment plant (TP) return flows, transmission losses and return flow losses to groundwater, reservoir losses to groundwater (Res), river tailflow into groundwater, and subsurface flow from river reaches (Rch), minus withdrawals by demand sites, subsurface flow to river reaches and groundwater overflow (net inflow. In addition, if linking to MODFLOW, there will be subsurface inflows from and outflows to other groundwater nodes.
EndMonthStorageGW = BeginMonthStorageGW
+ NaturalRechargeGW + 
DSReturnFlowDS,GW +
TPReturnFlowTP,GW
+ TransLinkLossToGroundwaterDS,GW
+ DSReturnFlowLinkLossToGroundwaterDS,GW+ TPReturnFlowLinkLossToGroundwaterTP,GW + 
ReservoirLossToGroundwaterRes,GW + 
RiverTailflowIntoGroundwaterRiver,GW + 
ReachFlowToGroundwaterRch,GW + 
OtherGroundwaterFlowToGroundwaterSrc,GW - TransLinkInflowGW,DS - GroundwaterFlowToReachGW,Rch
- 
GroundwaterFlowToOtherGroundwaterGW,Dest
The EndMonthStorage cannot exceed the groundwater node's storage capacity. Any excess will overflow, and be lost from the system. (If no data is entered for storage capacity, the capacity is unlimited and there cannot be any overflow.)
IF EndMonthStorageGW
> StorageCapacityGW THEN
OverflowGW = EndMonthStorageGW
- StorageCapacityGW
EndMonthStorageGW = StorageCapacityGW
ELSE
OverflowGW = 0
The amount withdrawn from the aquifer to satisfy demand requirements is determined in the context of all other demands and supplies in the system. The maximum withdrawals from an aquifer can be set (see Supply and Resources\Groundwater\Maximum Withdrawal), to model the monthly pumping capacity of the well or other characteristics of the aquifer that could limit withdrawals.
TransLinkInflowGW,DS
MaximumGroundwaterWithdrawalGW