Groundwater parameters should be applied to model the groundwater flow between an aquifer and the drainage system node.

Parameter Name | Description | Default Value |
---|---|---|

Aquifer | Aquifer object that lies below subcatchment (leave blank for no groundwater). | |

Receiving Node | The node name which receives groundwater from the aquifer | |

Surface Elevation [m] | Elevation of ground surface for the subcatchment (m or ft). | 0 |

Groundwater Flow Coeff. | Multiplier of the distance between actual and threshold GW levels | 0 |

Groundwater Flow Expon. | Exponent of the distance between actual and threshold level GW levels | 0 |

Surface Water Flow Coeff. | Multiplier of the distance between surface water level and threshold GW level | 0 |

Surface Water Flow Expon. | Exponent of the distance between surface water level and threshold GW level | 0 |

Surface-GW Interaction Coeff. | Multiplier of the product of GW height and surface water height above aquifer bottom. | 0 |

Fixed Surface water Depth [m] | Fixed depth of surface water at receiving node (ft or m) (set to zero if surface water depth will vary as computed by flow routing | 0 |

Threshold Groundwater Elev. [m] | Groundwater elevation that must be reached before any flow occurs (ft or m). leave blank to use the receiving node’s invert elevation. | |

Bottom Elevation [m] | Elevation of the bottom of the aquifer | |

Water Table Elevation [m] | Elevation of the water table in the aquifer at the start of the simulation | |

Unsat. Zone Moisture | Moisture content of the unsaturated upper zone of the aquifer at the start of the simulation (fraction). |

**Aquifer Name:**This field specifies the name of the aquifer object that describes the subsurface soil properties, thickness, and initial conditions for the subcatchment. Leaving it blank means the subcatchment won’t generate any groundwater flow.**Receiving Node:**This property designates the name of the node in the conveyance system that receives groundwater from the subcatchment.**Surface Elevation:**It represents the elevation of the subcatchment’s ground surface in feet or meters.**Groundwater Flow Coefficient (A1):**This coefficient (A1) is used in the groundwater flow equation and determines the rate of lateral groundwater flow as a function of groundwater and surface water levels.**Groundwater Flow Exponent (B1):**This exponent (B1) is part of the groundwater flow equation and affects the rate of lateral groundwater flow.**Surface Water Flow Coefficient (A2):**A2 is another coefficient in the groundwater flow equation, influencing the rate of lateral groundwater flow concerning surface water.**Surface Water Flow Exponent (B2):**B2, as part of the groundwater flow equation, determines how the rate of lateral groundwater flow responds to changes in surface water levels.**Surface-GW Interaction Coefficient (A3):**A3 is a coefficient in the groundwater flow equation that accounts for interactions between surface water and groundwater.**Surface Water Depth (HSW – HCB):**This property specifies the fixed depth of surface water above the receiving node’s invert in feet or meters. Set to zero if surface water depth varies as computed by flow routing.**Threshold Water Table Elevation (EB + HCB):**It indicates the minimum water table elevation that must be reached before any groundwater flow occurs. Leave it blank to use the receiving node’s invert elevation.**Aquifer Bottom Elevation (EB):**This is the elevation of the bottom of the aquifer below the specific subcatchment. Leave it blank to use the value from the parent aquifer.**Initial Water Table Elevation (EB + HGW):**Specifies the initial water table elevation at the start of the simulation for this subcatchment. Leave it blank to use the value from the parent aquifer.**Unsaturated Zone Moisture:**This property represents the moisture content of the unsaturated upper zone above the water table for this particular subcatchment at the start of the simulation, given as a volumetric fraction.

The Groundwater Flow Editor dialog is used to configure groundwater behavior within a subcatchment. It links the subcatchment to both a parent aquifer and a node in the conveyance system for groundwater exchange. This editor defines coefficients (A1, A2, B1, B2, and A3) in an equation that computes lateral groundwater flow based on groundwater and surface water levels:

Where QL represents lateral groundwater flow (in various units), HGW is the height of the saturated zone above the aquifer bottom, HSW is the height of surface water at the receiving node above the aquifer bottom, and HCB is the height of the channel bottom above the aquifer bottom.

Additionally:

GroundWaterFlow (QD): Defines percolation to deep groundwater using the equation QD = LGLR * HGW / HGS where LGLR is the lower groundwater loss rate parameter and HGS is the distance from the ground surface to the aquifer bottom.”