For the facilities in the biofilter box, the sub-flows are now calculated from these via stormwater and groundwater, respectively, so that in result report 4.2, not only the values of the total amount of outgoing pollution are obtained, but also specifically the part of this amount that is transported via stormwater and the part of this that is transported down to the groundwater.
The basis for this division of flows is the specified hydraulic conductivity for substructure / subsoil / terrace, with default value of 8.0 mm/h. The calculation takes into account that this velocity is not constant but consider the flow the conductivity gives through the facility’s ground and side surfaces. This flow’s share of total annual flow is calculated as the basis for the proportion of stormwater that flows down to the groundwater. This also requires the user to provide information on the length and side slope of the facility.