A water diverting device is used for fitting inside a porous surrounding wall of a vertical drainage pipe which is deeply inserted into the soil for collecting water from the ground level. The water diverting device includes a tubular wall having at least one slit, and a base wall having at least one drainage port. The drainage port is located at a higher level than a lower slit edge of the slit so as to have a lower level of water accumulated for passing through the slit and an upper open end segment of the porous surrounding wall, thereby soaking the soil near the ground level.