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- Determine the rainfall on the measure for the current time step.
- Determine the runoff from the measure inflow area to the measure for the current time step.
- Determine the initial interception storage of measure. Initial interception water budge budget includes interception storage at the end of previous time step + rainfall + runoff from measure inflow area in case runoff is defined to flow to interception layer.
- Determine the evaporation from the interception layer of the measure, limited by Penman evaporation.
- Determine the downward infiltration from the interception layer. Downward infiltration from the interception layer is only possible when the measure structures contain at least 2 layers.
Note: Downward infiltration calculation for a green roof is separately defined. - Determine the surface overflow from the interception layer of the measure.
- Determine the final interception storage on the interception layer of the measure.
- Determine initial storage in top storage layer of measure. When measure structure contains only 2 layers. This storage is zeros (when 2 layer — no top storage layer is involved, all the variable related to top storage layer will be zero.) When 3 layer, initial storage in top storage layer of measure is storage at previous time step + downward infiltration from interception layer.
- Determine transpiration from top storage layer of measure, limited by water availability and Penman evaporation multiplied with a predefined reduction factor.
- Determine the percolation from the top storage layer of the measure to the bottom storage layer of the measure.
Note: This variable is separately defined for green roof type measures. - Determine the final storage in the top storage layer of the measure, limited by the predefined storage capacity of the top storage layer of the measure.
- Determine the initial storage in the bottom storage layer of the measure.
- Determine the evapotranspiration from the bottom storage layer of the measure. Transpiration from the bottom storage layer can only occur when defined possible and when the transpiration capacity exceeds the transpiration from the top storage layer in case of 3 layers.
- Determine the percolation from the bottom storage layer of the measure to the groundwater. Specify whether this percolation is limited by the groundwater level or not. If not, the limitation will only be the saturated permeability. It is recommended to specify percolation being not limited by the groundwater level.
- Determine the controlled runoff from the bottom storage level of the measure. The controlled runoff can be modelled as either a constant flux or as a dynamically-computed flux that depends on a user defined drainage level and resistance.
- Determine the final storage of the bottom storage layer of the measure.
- Determine the overflow from the bottom storage layer of the measure if the bottom layer is completely filled.
- Determine the outflow from the measure to OW, UZ, GW, SWDS, MSS, Out
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