Here is an infographic of all water on Earth. Out of the total water, 97.5% is ocean; a mere 2.5% freshwater.
Out of that 2.5%, a whopping 68.7% is trapped in glaciers; 30.1% is in the form of groundwater; 0.8% is permafrost, and 0.4% is surface and atmospheric water.
That 0.4% of our global water is composed of: 67.4% freshwater lakes; 12.2% soil moisture; 9.5% in the atmosphere; 8.5% in other wetlands; 1.6% rovers, and 0.8% stored in plants and animals.. Infographic taken from WWAP 2006, based on data from Shiklomanov and Rodda 2003.
If for nothing else, this graph should teach us how little fresh water is available for human consumption. With such little water available for human use, we must use the water we do have access to efficiently, as to not waste it. Instead of looking at spending billions of dollars to purify and remove the salt from seawater, why not use technology that we already have to implement efficient usage of the water that is already available to us? After all, we have plenty to use. We just have a habit of wasting it.