The maximum residual error is the largest allowable value of residual error during an iteration. The solution is obtained when the residual error during an iteration in any computational node is less than the specified tolerance.
The value of the maximum residual error should be selected according to aquifer properties and the dimensions of the model. In practice the maximum residual error value will always be a compromise between accuracy and computing time. It is recommended to check the water balance carefully at the end of the simulation, but it should be emphasized that large internal water balance errors between adjacent computational nodes may not be detected. If large errors in the water balance are produced the maximum residual error should be reduced.