the stever is a tributary of the lippe which is fed by water out of the dortmund-ems canal and has a huge meaning for drinking water supply for the northern ruhr region. to balance the whole system the stever – after being fed out of the canal in senden – is backed-up in two water reservoirs (talsperre hullern and halterner stausee) of 32 mio. m³ capacity. two-thirds of the stever flow is discharged downstream; one-third is used by the drinking water supplier gelsenwasser ag for drinking water processing via soil infiltration from groundwater wells (of all together approximately 129 mio. m³/year). additionally the municipal utilities stadtwerke münster use water from the dortmund-ems canal to supply the groundwater wells for drinking water processing. in total, via several water works annually 250 mio. m³ of water are transported in pipework from the ruhr to the area at the canals.