This study aims to assess the impact of climate change on water resources in the high Oum Er Rbia basin. To achieve this goal; four stations were studied: Dchar el Oued, Taghzout, Taghat and Tamchachte. The difference in the annual mean and annual variations in hydroclimatic factor show that during the period of 1974-2001, the area has very dry and wet years, with excessive periods (1976/1977, 1978/1979 and 1995/1996) and with passive periods (1983/1984, 1992/1993 and 1994/1995). The period of 1974-2001 was characterized by a percentage of 40.7% of wet years and a percentage of 59.3% of dry years. The annual rates of upper Oum Er Rbia basin during the period of 1974-2001 for the Dchar El Oued station indicate a height of average annual water 202.2 mm, while the average annual rainfall in the basin, for the same period of observation is 536.0 mm. It can be inferred that the loss of water: infiltrated, evaporated maintained in the soil or used for irrigation is 333.8 mm or 62.27% of the precipitation. Finally, the general tendency of the high Oum Er Rbia basin is toward drought whose frequency has increased in recent decades to 32.6%.