The Middle Atlas, water tower of Morocco, is largely composed of a limestone substratum, which implies groundwater redistribution towards karstic aquifers. In its central part, the Middle Atlas is drained by Sebou River upstream. Many authors have studied this redistribution essentially from the group of springs flows downstream of the Upper Sebou catchment and from the upstream of the Oum Er Rbia basin which drains the southern Middle Atlas. We refine and discuss these proposals on the basis of new results concerning hydrological balances calculated from flow data available at 5 hydrometric gauges and the spatialization of climatic variables P and ET in this area. It seems that 30% of the rainfall infiltrated into the Upper Sebou basin is transferred outside the basin, 25% to the Oum Er Rbia and 5% to the Saïs plain. We hypothesize that the group of springs located at the extreme downstream end of the basin and making up a third of the Sebou flow at its outlet from the Middle Atlas is fed by infiltration into the upstream sub-basins that are right bank tributaries of the main course of the Sebou.