Model equations

The model equations are presented here. Each model setup represents specific a combination of equations. We refer to Constant model parameters and Model variables representing the described parameters and variables as objects (e.g. float, array).

While using jax, jax-mpi or jax-gpu (-b) to compute the solute transport, the default float type of float32 needs to be changed to float64 (–float-type). Currently, using float32 leads to numerical instabilities.

` python svat_transport.py -b jax --float-type float64 `

Time-stepping

Three different time-stepping schemes are available to solve the equations. The time-stepping depends on the model setup:

• adaptive time-stepping is used for long-term hydrologic modelling (i.e. modelling the water balance over multiple years)

• fixed time-stepping is used for short-term hydrologic modelling (i.e. modelling a single rainfall event)

• fixed time-stepping with internal substepping is used for solute transport models