Viewed from space, as in NASA’s “Blue Marble” below, one quickly recognizes that water covers most of the earth’s surface. Even on land, the hydrologic cycle is responsible for its dominant features, from glaciers and rivers to jungles and deserts. Below the land surface, groundwater is found almost everywhere at some depth. Earth truly is a hydroplanet.
Yet most of Earth’s water is unsuitable for human use. Over 97% is saltwater, and of the remaining freshwater, all but about 1% is frozen or underground. Even the world’s vast lakes and long rivers make up only a small fraction of all freshwater. What remains is sometimes too remote or too little.
In this context on Earth Day, water becomes more precious than ever, calling for sustainable solutions to meet both human and environmental needs.