The model contains eight parameters, which are shown in the first three columns of Table 2, and the overall forecasting procedure is presented in Figure 4(b) with detailed descriptions as follows:
Retrieve the evaporation constant and daily rainfall amounts during N days before the forecasting day.
Estimate the soil moisture of the two layers from N day before to 1 day before.
- Calculate the accumulated inflow flood volume based on the surface and subsurface runoff.where IF is the accumulated inflow flood volume (m3) and Rl is the total runoff volume (mm).1
- If the forecasted flood level based on reservoir stage–storage curve is higher than the FLWL during the flood season, flood discharge is required immediately. The total outflow volume can be calculated as follows:where OF is the total outflow volume (m3), vi is the flood discharge during a particular period (m3/s) and ti is the corresponding duration (s).2
Finally, the discharged water level is obtained by the actual change of storage capacity.
Table 2
Model parameters and their values for the Hengshan Reservoir
| Parameter | Description | Unit | Value |
|---|---|---|---|
| Wm | Maximum antecedent soil moisture | mm | 90.4 |
| WUm | Maximum antecedent moisture of the upper soil layer | mm | 31.8 |
| WLm | Maximum antecedent moisture of the lower soil layer | mm | 58.6 |
| N | Number of days before for soil moisture estimation | 14 | |
| Rb | Daily subsurface runoff volume | mm | 5.3 |
| E | Evaporation consumption on a non-rainy day | mm | 4.2 |
| A | Catchment area | m2 | 1.548 × 108 |
| OFmin | Minimum daily discharge amount | m3 | 2.5 × 105 |
| Parameter | Description | Unit | Value |
|---|---|---|---|
| Wm | Maximum antecedent soil moisture | mm | 90.4 |
| WUm | Maximum antecedent moisture of the upper soil layer | mm | 31.8 |
| WLm | Maximum antecedent moisture of the lower soil layer | mm | 58.6 |
| N | Number of days before for soil moisture estimation | 14 | |
| Rb | Daily subsurface runoff volume | mm | 5.3 |
| E | Evaporation consumption on a non-rainy day | mm | 4.2 |
| A | Catchment area | m2 | 1.548 × 108 |
| OFmin | Minimum daily discharge amount | m3 | 2.5 × 105 |