Why is only a small share of Earth's total water available as fresh surface water?

The vast majority of Earth's water is not available as fresh surface water because it is either stored in the oceans or locked away in polar ice caps and glaciers.1

Specifically, approximately 96.5 percent of Earth's water is held in oceans, where high concentrations of dissolved minerals and salts make it unsuitable for most human uses. An additional portion is trapped as ice, which is not readily accessible for immediate consumption. While groundwater constitutes a significant share of liquid fresh water, much of it is located at great depths, making extraction technically difficult and economically expensive.213

Consequently, less than 1 percent of Earth's total water exists as accessible liquid fresh water. Although this amount is sufficient to meet global human needs, it is not uniformly distributed across the planet, and its availability is further constrained by factors such as water pollution, seasonal variability, and the distance between water sources and population centers.14