1809.9 km³/1,262,736,900 km³ = 0.00014%
(of the global cycle)

But, 97% is salt water, and 2% is in polar ice caps.
Only 0.007% of water on Earth is readily available!

1809.9 km³/88384.6 km³ = 1.2%

What's critical is human needs.