ERROR 110:
Ground elevation is below water table for Subcatchment xxx.
Error 110 : The ground elevation assigned to a Subcatchment's groundwater parameters cannot be below the initial water table elevation of the aquifer object used by the Subcatchment.
1. Description
The ground elevation assigned to a Subcatchment's groundwater parameters cannot be below the initial water table elevation of the aquifer object used by the Subcatchment.
So, ERROR 110 occurs during the model validation process, before the simulation starts. It indicates that the ground elevation assigned to a subcatchment is equal to or lower than the initial water table elevation defined for the associated aquifer.
2. Technical Background
The groundwater module in SWMM requires a physically consistent vertical structure (Figure 1):
- Ground Surface Elevation – top of unsaturated zone (Subcatchment Groundwater dialog)
- Initial Water Table Elevation – starting depth of saturated zone (Aquifer object)
- Aquifer Bottom Elevation – base of modeled aquifer (Aquifer object)
Constraint: Ground Surface Elevation > Initial Water Table Elevation > Aquifer Bottom Elevation
This error occurs when ground surface elevation is lower than the initial water table. Such a condition is not physically realistic because it would imply that the water table is above the ground surface. As a result, SWMM aborts with ERROR 110 rather than attempting a simulation on invalid geometry.
3. Resolution
Work through the following steps in order. First, rule out data, datum, and unit inconsistencies. Then verify the groundwater elevation relationship for the flagged subcatchment. If the values are correct and the site has a naturally shallow water table, use Step 4 rather than forcing unrealistic elevation adjustments.
Table 1 : Resolution steps
Step | Action | Why It Helps |
|---|---|---|
1 | Review source data, units, and vertical datum
| Mixed units, datum inconsistencies, or source data errors can make otherwise valid values appear inconsistent. |
2 | Identify the flagged subcatchment
| Identifies the specific values involved in the validation failure. |
3 | Verify the elevation hierarchy
| Confirms that a positive unsaturated zone exists above the saturated groundwater zone. |
4 | Adjust high water table or wetland conditions
| Maintains SWMM validation requirements while representing near-surface groundwater conditions. |