How Much Fresh Water Is Available for Human Use?

Of Earth's total water, only 2.5% is fresh. Of that, most is locked in glaciers, ice caps, and deep aquifers. Only ~1% of all fresh water (0.025% of total water) is readily accessible—rivers, lakes, shallow groundwater. This tiny fraction is unevenly distributed, and pollution, overuse, and climate change further reduce usable supply. Wise management is existential.