What Is Water? - Freshwater

Despite the enormous amount of water that surrounds us, only about 3% of it is freshwater and, therefore, suitable for use by land-based animals, plants, and humans. Almost four-fifths of freshwater is frozen in ice caps and glaciers, and therefore not accessible. The availability of freshwater depends on many factors: climate, location, rainfall, and local activity. The world's freshwater lakes contain about 30,000 cubic miles of water, and about 300 cubic miles of freshwater are found in the world's rivers and streams. Together, lakes, rivers, and streams make up about 0.009% of total water on earth. Groundwater (subsurface water) totals about one million cubic miles or 0.52% of the total water supply. Figure 1.5 shows the comparative volumes of these freshwater sources.