Water in the Atmosphere and Rivers
At any given moment, the atmosphere does contain more fresh water than all the planet’s rivers. The USGS estimates about 12,900 km³ of water in the atmosphere, compared with roughly 2,120 km³ in rivers. Both reservoir estimates have uncertainty, but the difference is large.
If all atmospheric water condensed at once and fell evenly over Earth’s surface, it would form a precipitation layer about 2.5 cm deep—roughly one inch. This is a thought experiment: atmospheric water is continually transported, evaporated, and precipitated, and actual precipitation is not distributed evenly.