# HydroGeoSphere/Travel Time Probability

## Find zero age zonesEdit

**HydroGeoSphere** will automatically find the inlet (or outlet for the backward problem) nodes and assign the proper initial condition (or boundary condition for the moment equations). This option is valid for the case of age/life expectancy computations at aquifer scale, in which case each node belonging to the inlet/outlet zone is to be assigned a zero age/life expectancy condition.

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## Zero travel timeEdit

Assigns a zero travel time condition for the chosen nodes.

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