Water covers nearly three-quarters of the earth’s surface. It is mainly in oceans but is also found as rivers, lakes, snow and glaciers. Freshwater lakes and rivers, ice and snow, and groundwater hold only 2.5% of the world’s water, which most of it (about 70%) comes from glaciers and permanent snow cover. Of the total world’s freshwater supply, 30% is groundwater, including soil moisture, wetland and permafrost. By comparison, saltwater oceans and seas contain 97.5% of the world’s water supply.