THE HYDROSPHERE EFT 2173 INTRODUCTION • A hydrosphere (from Greek - hydor, "water" and - sphaira, "sphere") in physical geography describes the combined mass of water found on, under, and over the surface of a planet. • The total mass of the Earth's hydrosphere is about 1.4 × 1018 tonnes, which is about 0.023% of the Earth's total mass. About 20 × 1012 tonnes of this is in the Earth's atmosphere (the volume of one tonne of water is approximately 1 cubic metre). • Approximately 75% of the Earth's surface, an area of some 361 million square kilometres (139.5 million square miles), is covered by ocean. The average salinity of the Earth's oceans is about 35 grams of salt per kilogram of sea water (35 ‰). THE HYDROSPHERE All of the water found on Earth Forms of water Forms of water Distribution of Water on Earth (% statistic) Distribution of Water on earth (% statistic) reservoir oceans Water masses at Earth's surface volume (in cubic kilometres) 1,338,000,000 percent of total 96.5 ice caps, glaciers, and permanent snow 24,064,000 1.74 ground ice and permafrost groundwater (total) groundwater (fresh) groundwater (saline) lakes (total) lakes (fresh) lakes (saline) soil moisture atmosphere* swamp water rivers biota total** 300,000 23,400,000 10,530,000 12,870,000 176,400 91,000 85,400 16,500 12,900 11,470 2,120 1,120 1,409,560,910 0.22 1.69 0.76 0.93 0.013 0.007 0.006 0.001 0.001 0.0008 0.0002 0.0001 101.67 *As liquid equivalent of water vapour. **Total surpasses 100 percent because of upward rounding of individual reservoir volumes. URL: https://www.britannica.com/science/hydrosphere Access Date: June 06, 2020 Source: Adapted from Igor Shiklomanov's chapter "World Fresh Water Resources" in Peter H. Gleick (ed.), Water in Crisis: A Guide to the World's Fresh Water Resources, copyright 1993, Oxford University Press, New York, N.Y. Table made available by the United States Geological Survey. Freshwater • Smaller bodies of water (3% on earth ) • Fresh water is water that not salty and has little or no taste , colour or smell. • Most of it at polar regions and glaciers (68%), some groundwater (30%), only little in water vapours an lakes or rivers (2%). • Examples: • glaciers • Streams • Ponds • Lakes • rivers Iceberg • Iceberg: a large piece of freshwater ice floating in open waters • Icebergs start out as part of a glasier • 80% of an iceberg is under water Wetland An area where the water table is at, near or above the land surface long enough during the year to support adapted plant growth. • Swamp: a wetland dominated by trees • Bogs: a wetland dominated by peat moss • Marshes: a wetland grasses dominated by Groundwater • Water that is held underground because it has soaked into the ground and percolated (water that is filter by porous rocks. • Water the seeps through soil and gets stored in underground rock formations called aquifers. • Surface of land where water seeps is called recharge zone. Saltwater • Larger bodies of water are saltwater (97% of earth) • Saltwater is clear and taste salty.- higher in hot and closed seas. • Temperature: higher in the surface, colder in the deep. • Examples: • Oceans • Gulfs • Seas Water salinity • Salt comes from erosion from rocks on land over millions of years and underwater volcanic eruptions • Salinity can vary depending on depth of ocean & areas of evaporation • E.g: estuary-where freshwater river meets ocean. • Salt water is more dense than fresh water • Ocean water is 3.5% salt water salinity, defining freshwater, brackish water, saltwater, and brine water Transformation of water • Exothermic – having to release heat to change state of matter • Exothermic changes • Freezing –liquid to solid • Condensation – gas to liquid • Deposition – gas to solid Endothermic-having to take in heat • Endothermic Changes • Melting – solid to liquid • Evaporation – liquid to gas How is the water is moved and maintained on earth? • The un-ending circulation of the Earth ‘s water is called the hydrologic or water cycle • The water present on the earth today is the same water that was formed with the planet itself • The amount of water cannot be increased or decreased. The amount of water on earth stays the same. Hydrologic cycle • This cycle consists of a group of reservoirs containing water, the processes by which water is transferred from one reservoir to another (or transformed from one state to another), and the rates of transfer associated with such processes. • These transfer paths penetrate the entire hydrosphere, extending upward to about 15 km in Earth’s atmosphere and downward to depths on the order of 5 km in its crust. Components in Hydrologic (Water) Cycle • Evaporation • Heated by sun and turns into water vapor • Comes from bodies of water, plant and animals • Condensation • Water vapor forms droplets on dust particles, form clouds when they collide and stick • Precipitation • Large droplets fall from clouds • Can be rain, snow, sleet or hail • Runoff • Water can run off land into nearest body of water • Water can percolate through layers of soil and get stored underground in aquifers. The summary 1. Sun heats the water on the surface of earth 2. Freshwater evaporates into atmosphere as water vapor (salt in ocean stays behind) 3. Water vapor cools & condenses on dust particles to form clouds 4. Water falls back to Earth as precipitation in the form of rain, sleet, snow or hail 5. Precipitation that hits surface either gets absorbed into ground, stay trapped as standing water or moves downhill as run-off back into lakes, ponds, rivers, streams oceans The Hydrologic Cycle (Water Cycle) Importance of earth’s hydrosphere The hydrosphere plays a very important role in the evolution of life, as well as in weather, and erosion. Helping to regulate temperatures on earth so that they stay within a range that is acceptable for life to exist. Ocean currents also help to disperse heat. Regulating climate One of water's unique characteristics is its high specific heat. This means that water takes a long time to heat up and also a long time to cool down. This is important in helping to regulate temperatures on earth so that they stay within a range that is acceptable for life to exist. Ocean currents also help to disperse heat. The hydrosphere provides an important place for many animals and plants to live. Water provides a habitat The hydrosphere provides an important place for many animals and plants to live. Many gases (e.g. CO2, O2), nutrients e.g. nitrate (NO−3), nitrite (NO−2) and ammonium (NH+4) ions, as well as other ions (e.g. Mg2+ and Ca2+) are dissolved in water. The presence of these substances is critical for life to exist in water. Water is a part of living cells Each cell in a living organism is made up of almost 75% water, and this allows the cell to function normally. In fact, most of the chemical reactions that occur in life, involve substances that are dissolved in water. Without water, cells would not be able to carry out their normal functions and life could not exist. Humans use water in a number of ways. Drinking water is obviously very important, but water is also used domestically (e.g. washing and cleaning) and in industry. Water can also be used to generate electricity through hydropower.
