# constraints Section

This section configures **constraints** for the model, including **elevation clamping**, **nudging**, and **relaxation parameters**.

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 | **Parameter** | **Description** |
 |---------------|----------------|
 | `use_internal_specifications` | Flag to use internal specifications for constraints (`TRUE`, `FALSE`). |
 | `elevation_constraint_file` | File containing elevation constraints (clamped or nudging). |
 | `constraint_method` | Method for constraints (`CLAMPED`, `NUDGING`). |
 | `constraint_start` | Start time for applying constraints (default: `0 h`). |
 | `relaxation_time_scale` | Time scale for nudging relaxation (default: `300 s`). |
 | `relaxation_length_scale` | Length scale for nudging relaxation (default: `1000 m`). |
 | `relaxation_extent` | Extent length for nudging relaxation (default: `1000 m`). |
 | `max_data_gap` | Maximum allowed data gap for constraints (default: `600 s`). |
 | `apply_spatial_gradient` | Flag to apply spatial gradient in constraints (`TRUE`, `FALSE`). |
 | `echoing_file_template` | Template for echoing model values at constraint locations. |
 | `echoing_interval` | Interval for echoing constraint values (default: `300 s`). |