PDM Descriptor objects are used to define the rainfall-runoff parameters for a PDM subcatchment.
This table describes all the data fields used to define a PDM Descriptor.
Fields that are common to the majority of objects can be found in the Common Fields topic.
PDM Descriptor Data
Database Table Name: hw_pdm_descriptor
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Field Name |
Description |
Database Field |
Size |
Precision |
Default |
Error Lower Limit |
Error Upper Limit |
Warning Lower Limit |
Warning Upper Limit |
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| Descriptor ID | Name of the PDM Descriptor object. | descriptor_id | Text | 64 | 0 | ||||||||||||||||||||||||
| Rainfall and evaporation |
Method used to calculate rainfall and evaporation:
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re_type | Text | 50 | 0 | Standard | 0 | 0 |
0 |
0 |
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| Rainfall factor | Multiplying factor to be applied to measured rainfall to obtain an average rainfall across the catchment. | rainfac | Double | 3 | 1 | 0 |
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| Evaporation exponent | Exponent in evaporation function. | be | Double | 3 | 2.5 | 0 |
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| Infiltration rate parameter | Enabled when Rainfall and evaporation set to Infiltration or Infilt_frozen. | kinf | Double | I | 3 | 0 | 0 | ||||||||||||||||||||||
| Frozen infiltration rate parameter | Enabled when Rainfall and evaporation set to Infilt_frozen | kfreeze | Double | 3 | 0 | 0 | |||||||||||||||||||||||
| Frozen time constant | Enabled when Rainfall and evaporation set to Infilt_frozen | kt | Double | 3 | 0.5 | 0 | |||||||||||||||||||||||
| Soil moisture distribution |
Method used to calculate soil moisture distribution:
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smd_type | Text | 50 | 0 | Pareto | 0 | 0 |
0 |
0 |
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| Minimum storage capacity | Minimum storage capacity in the catchment. | cmin | Double | SC | 3 | 1.5 | 0 |
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| Maximum storage capacity | Maximum storage capacity in the catchment. | cmax | Double | SC | 3 | 75 | 0 |
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| Pareto exponent |
Exponent of Pareto distribution controlling spatial variability of store capacity. Enabled when Soil moisture distribution is set to Power. |
b | Double | 3 | 1 | 0 | |||||||||||||||||||||||
| Recharge/runoff |
Method used to calculate recharge and runoff:
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rr_type | Text | 50 | 0 | Standard | 0 | 0 |
0 |
0 |
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| Ground recharge time constant |
Groundwater recharge time constant. Enabled when Recharge/runoff set to Standard. |
kg | Double | 3 | 1000 | 0 |
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| Soil tension storage capacity |
Threshold storage below which there is no drainage; water being held under soil tension. Enabled when Recharge/runoff set to Standard. |
St | Double | SC | 3 | 0 | 0 |
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| Recharge function exponent |
Exponent of recharge function. Enabled when Recharge/runoff set to Standard. |
bg | Double | 3 | 1 | 0 |
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| Initial soil moisture proportion of max | Enabled when Recharge/runoff set to Splitting or Split_unrest. | theta | Double | 3 | 0.7 | ||||||||||||||||||||||||
| Surface flow runoff proportion |
Runoff factor controlling the split of rainfall to surface and groundwater storage routing when no soil recharge is allowed. Enabled when Recharge/runoff set to Splitting or Split_unrest. |
alpha | Double | 3 | 0.4 | 0 | 1 (Splitting only) | ||||||||||||||||||||||
| Baseflow store runoff proportion |
Proportion of runoff entering the baseflow store. Enabled when Recharge/runoff set to Split_unrest. |
beta | Double | 3 | 0 | ||||||||||||||||||||||||
| Groundwater deficit ratio threshold | Enabled when Recharge/runoff set to Demand_based. | alpha_d | Double | 3 | 0.5 | 0 | |||||||||||||||||||||||
| Maximum recharge rate | Enabled when Recharge/runoff set to Demand_based. | qsat_d | Double | I | 3 | 2 | 0 | ||||||||||||||||||||||
| Groundwater demand factor exponent | Enabled when Recharge/runoff set to Demand_based | beta_d | Double | 3 | 1 | ||||||||||||||||||||||||
| Surface store |
Method used to calculate surface storage:
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ss_type | Text | 50 | Linear_cascade | 0 | 0 |
0 |
0 |
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| Linear reservoir 1 time constant | Linear reservoir time constant | k1 | Double | 3 | 10 |
0.00025 (Linear cascade) 0 (surface storage except linear cascade) |
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| Linear reservoir 2 time constant | Enabled when Surface store set to Linear_cascade | k2 | Double | 3 | 0 | 0.005 |
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| Interflow |
Method used to calculate interflow (lateral flow through soil layers). If Interflow is set to a value other than None, Recharge and runoff must be set to Standard and Soil moisture deficit must be set to Pareto.
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if_type | Text | 50 | 0 | None | 0 | 0 |
0 |
0 |
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| Interflow time constant |
Enabled when Interflow set to choice other than None. |
ki | Double | 30 | 3 | 30 | 0 | ||||||||||||||||||||||
| Interflow factor | Enabled when Interflow set to choice other than None. | fi | Double | 3 | 0 | 0 | 1 | ||||||||||||||||||||||
| Baseflow store |
Method used to calculate baseflow :
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bs_type | Text | 50 | 0 | Cubic | 0 | 0 |
0 |
0 |
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| Baseflow time constant |
Constant used for all baseflow modelling methods. The metric unit used for the baseflow time constant is: h mm^(M-1), where M is the exponent in the baseflow storage equation |
kb | Double | 3 | 500 | 0 |
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| Time delay | Constant time delay applied to output flow | tdly | Double | 3 | 0 | 0 |
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