Distributed acceptable load for stormwater between different stakeholders within the catchment
It is possible in StormTac Web to distribute the acceptable load and the required treatment of the receiving water between different stakeholders by creating different sub catchment areas (A1, A2, …).
One can input agricultural land in one area, the Transport Administration’s roads in another, urban areas in a third and you can also add land uses for one municipality in one area and for another municipality in another. StormTac Web then calculates a distributed acceptable load for each stakeholder, you get a division of responsibilities.
This gives an interesting basis regarding for example how the required treatment (kg/year) can be distributed between different municipalities whose stormwater loads the recipient.

Distributed acceptable load for point flows between different stakeholders
In addition to stakeholders that contribute to stormwater loads, there may be other actors connected to a recipient, calculated as point flows in the StormTac Web model. It can be wastewater treatment plants, pumping stations that overflow (CSO’s) or point flows from upstream receiving waters.
Such point flows may not be the responsibility of the municipality/municipalities (within the catchment area) to treat. It could make unreasonable and unfair demands. The municipalities located upstream the receiving water that gives a point flow to the receiving water, the pumping stations and wastewater treatment plants that add loads to the recipient also need to be responsible for their part of the treatment need and get an acceptable load to relate to.
As an example, a wastewater treatment plant that gives a certain load to the recipient gets an assigned treatment need (kg/year) and an acceptable load (kg/year) that can be led out to the recipient (a watercourse, a lake or a sea).
The model can be used to simulate an expansion of the plant and see what change it entails in terms of treatment needs and acceptable load. The plant can be designed according to this, as well as any subsequent wetlands or the like.