Consideration of Ponds

A possible water retention at the surface in shallow ponds can be defined for each grid cell by defining such a maximum pond depth ("dam height") in a pond grid. A maximum pond depth of 0 means that there will be no water retention by ponds on this cell. On the other hand, if a pond depth of > 0 m is defined, surface runoff will be created only if the amount of water on the surface exceeds the maximum pond depth and no water can infiltrate.

Note that evaporation losses will be taken directly from a pond if there is enough water in it instead of from the soil. This is mainly to avoid numeric stability problems when running the groundwater model.

The pond grid is also used for the lake model. Here, the ponds define the maximum lake depth. This means that a lake is nothing more than a connected area of cells with pond values > 0 (Of course, a lake is specially treated in the lake module by balancing inputs and outputs and the actual content etc., see lake module).