REBECK-LZ is used to determine the volumes of rainwater retention basins required for a given exceedance frequency (DWA-A 117, 04/2006). It takes the complete precipitation continuum including all dry periods into account. The program shows the start and duration, the maximum storage volume as well as the overflow and drainage volumes for all damming events. The statistical evaluation of all accumulation events results in the maximum storage volume required for any recurrence times.