For unconfined surface water bodies, the hydraulic head (or potential \(\Psi\)) is given by the water level above the reference height. To use the potential as a driving force for gradient based connections, a relation between the stored volume (the integrated state variable in cmf) and the water level needs to be present.

OpenWaterStorage is the class for water storages containing free surface water. An OpenWaterStorage owns therefore functional description of the relationship between stored volume \(V\) and the height above the relative water depth \(h\).

\[Psi = h + z = f(V) + z \]

\(f(V)\) is given by a child class of IVolumeHeightFunction.

Hydraulic head in surface water bodies