![]() How does Earth maintain its supply of fresh water? If you needed drinking water in an emergency, how could you turn salt water into fresh water? Synopsis: Of all the water that covers 71 percent of Earth’s surface, 97.5 percent is salt water and only 2.5 percent is fresh. The water cycle creates Earth’s fresh water. Trap rising water vapor, allow it to condense on a surface, and drain it into something that you can drink from. Instead, find a way to make your own cloud. To neutralize it, your organs will draw water from the rest of your body, leading to rapid dehydration. Here’s a practical tip: If you ever find yourself in a dire situation with no fresh water, remember this distillation process.įirst, never drink seawater it’s four times saltier than blood. ![]() That brief, shining moment as surface fresh water has made virtually all land-based life possible, for hundreds of millions of years. The part that falls on land flows downhill, eventually into rivers that carry it back into the sea, to become salty again. Since Earth is mostly ocean, most rain falls in the ocean. In the atmosphere, water condenses on airborne particles and rains down again. In the phase change from liquid to gas, water leaves salt and all impurities behind. Heat and wind turn seawater into water vapor. ![]() That leaves just 1 percent of Earth’s fresh water on the surface.įrom all that salt water, how does this tiny fraction of surface fresh water come to be? It’s a process of natural distillation. Of that, 99 percent is locked up in glaciers and underground aquifers. Forest Service (public domain), via Wikimedia CommonsĮarth is mostly covered with water, and most of that is ocean. The provincial record is held by the Churchill River in central Labrador which discharges an average of almost 2000 cubic metres per second in June.Rain in the Cleveland National Forest in Southern California. In May, the month of maximum discharge in the Gander River (in central Newfoundland), the mean discharge is more than 250 cubic metres per second. John's, the capital of Newfoundland and Labrador, drains a small basin and the mean rate of flow in April is less than 5 cubic metres per second. The Waterford River, that runs through St. The volume of water discharged by a stream is also affected by the size of the drainage basin. In central and southern parts of the island, where precipitation can fall as rain during the winter, the winter streamflow minimum is less marked than the summer minimum. In Labrador and the northern parts of the island where winters are long and severe, this is the season of minimum streamflow. In winter, when temperatures fall below freezing and precipitation falls as snow, no surface water reaches the streams and flow decreases again. Soon the soil holds as much water as it can (it is saturated), and the surplus reaches the streams whose flow increases. With the approach of fall evapotranspiration decreases, and in the southern part of the island precipitation increases. ![]() Man-made reservoirs on dammed streams function like natural lakes to reduce peak run-off and maintain flow during the summer. Lakes in a streams's course store some of the spring run-off and help to maintain flow as do springs fed by groundwater. Although stream flow is low during the later part of the summer, streams rarely dry up completely. Farmers and gardeners know that the soil is much drier in summer than in spring or fall this is the result of high evapotranspiration during the growing season and means that very little of the rain that falls in summer reaches a stream. Evapotranspiration is at a maximum in summer, when temperatures are higher and plants are growing strongly. ![]()
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