Saturated Zone Storage

The saturated zone may receive inflow $q_{uz}$ from the unsaturated zone as well as saturated zone flow from upslope elements $q_{sz}^u$.

Saturated zone outflow is denoted by $q_{sz}$. Another possible outflow occurs when the saturation zone deficit drops below a given threashold value $D_{thr}$. If so, saturation runoff $q_{sr}$ is routed to downslope element surfaces.

The balance equation for the saturated zone deficit is

$\Delta D_{sz} = (-q_{uz} - q_{sz}^u + q_{sz} + q_{sr})\Delta t$.