Water is a renewable but limited resource because of anthropogenic factors and the worsening rainfall that reduce availability. The West Africa in general and the Watershed of Niger in particular is experiencing a downward trend of their rainfall regime. It is in this context that the present study is to investigate which on surface water and groundwater resources in the the Watershed of Niger in Benin. The methodology is based on the interpretation of rainfall data, hydroecoregions map design highlighting the availability of surface water followed by a geological photo-interpretation for a better knowledge of infiltration areas. The results of this study showed a high availability of surface water resources of 54.22% of the basin area. The low slope gradient so that material of the fracturing network predisposes the basement of the basin to a good availability for groundwater. Thus, the flow rate (<5 m3/s) developed by implanted drilling shows that the whatershed of Niger has significant amount of groundwater especially in the North East, where the developed flow rates exceed 83 m3/s.