This image will give you more idea of how much water there is on the surface in terms of spherical volume.
http://water.usgs.gov/edu/pictures/full-size/global-water-vo...
http://water.usgs.gov/edu/pictures/full-size/global-water-vo...
1. All water (largest sphere)
2. All of Fresh water.
3. Fresh water in lakes and rivers.
Reference: http://water.usgs.gov/edu/gallery/global-water-volume.html