Water Balance (WaterDist_Module)

[putupass]

I am currently studying SUEWS Spatial model using UMEP via QGIS, which compare mostly green (impervious, forest) grid and urban (50% impervious and 50% pervious) grid. I would like to discuss and ask some questions about the calculations in WaterDist_Module (https://github.com/UMEP-dev/SUEWS/blob/master/src/suews/src/suews_phys_waterdist.f95)

1. Based on the module, SurplusEv is transferred from impervious to pervious surfaces (line:264). In urban grids, Ev tends to be higher due to the presence of buildings. This surplus is used to evaporate water from pervious surfaces and prevent saturation. In contrast, in green grids (e.g., forest areas), Ev is generally lower, that mechanism does not happen, and the soil saturates more easily. As a result, the computed runoff often appears smaller in urban grids than in green (forest) grids, which seems counterintuitive. Was this outcome intended by the model?
2. Does this scheme account for separate interception processes between water retained on the ground surface and on the upper surface (e.g., canopy such as leaves, etc.)?
3. In line 324, when SoilStorage + State_Out ≥ 0, the soil storage is reduced by the water deficit so that State_Out = 0. However, if the condition is not met (SoilStorage + State_Out < 0), why is evaporation immediately set to zero (Ev = 0)? Was it intended that the water deficit is not partially reduced by the available soil storage? For example,
   Ev = Ev - (ABS(State_Out(is)) - SoilStorage(is));
   State_Out(is) = 0.0;
   SoilStorage(is) = 0.0;
   to reflect partial fulfillment of the deficit?
   Or have I possibly overlooked a part of the code that already addresses this condition?

Thank you.