1. GEO 200: Physical Geography The Hydrosphere

2. Rev. 15 April 2006The Hydrosphere2 The hydrosphere The hydrosphere is the most pervasive and least well defined of the four spheres of the physical environment. –The hydrosphere includes liquid water in oceans, lakes, rivers, swamps, groundwater, and raindrops; frozen water in snow, sea ice, and glaciers; and water vapor. The hydrosphere has significant overlap with the lithosphere, biosphere, and atmosphere. –Most interactions among the spheres occurs via the hydrologic cycle.

3. Rev. 15 April 2006The Hydrosphere3 The nature of water, part 1 Water as a substance is commonplace but unique. Water is both the most distinctive and the most abundant substance on Earth. Water’s structure is simple, two hydrogens bonded to one oxygen. Surface water makes up more than 70% of surface.

4. Rev. 15 April 2006The Hydrosphere4

5. Rev. 15 April 2006The Hydrosphere5 The nature of water, part 2 It comes in three states – solid, liquid, and gas – and can change from one state to another. In each of the processes by which water changes state, there is a gain or loss of heat. –Freezing is the process by which liquid water is converted to ice, thus giving off heat. –Melting is the process by which ice is converted to liquid water, thus absorbing heat. –Condensation is the process by which water vapor is converted to liquid water, thus giving off heat.

6. Rev. 15 April 2006The Hydrosphere6 The nature of water, part 3 State changes (continued) –Evaporation is the process by which liquid water is converted to water vapor, thus absorbing heat. –Sublimation is the process by which water vapor is converted directly to ice, or vice versa. Water has many unusual properties: –It is liquid at ordinary Earth temperatures; –It has great heat capacity (it takes a lot of energy to raise the temperature of water and water gives off a lot of energy when it cools);

7. Rev. 15 April 2006The Hydrosphere7

8. Rev. 15 April 2006The Hydrosphere8

9. Rev. 15 April 2006The Hydrosphere9 The nature of water, part 4 Water has many unusual properties (continued) –Water is densest at its liquid state and expands while cooling; –Water is known for its capillarity, a function of cohesion among water molecules and adhesion of water molecules to other substances; Capillarity is the action by which water can climb upward in restricted confinement as a result of its high surface tension and thus the ability of its molecules to stick closely together.

10. Rev. 15 April 2006The Hydrosphere10

11. Rev. 15 April 2006The Hydrosphere11 The nature of water, part 5 Water has many unusual properties (continued) –Water has tremendous ability to dissolve other substances; This property is perhaps the most significant. –It allows water to function as a weak acid. This property also means water in nature nearly always impure as it contains various other chemicals besides its hydrogen and oxygen atoms.

12. Rev. 15 April 2006The Hydrosphere12 Hydrologic cycle, part 1 Water is distributed very unevenly around Earth. Less than 1% of Earth’s total moisture is involved in the hydrologic cycle. The hydrologic cycle is a series of storage areas interconnected by various transfer processes, in which there is a ceaseless interchange of moisture in terms of its geographical location and its physical state.

13. Rev. 15 April 2006The Hydrosphere13

14. Rev. 15 April 2006The Hydrosphere14

15. Rev. 15 April 2006The Hydrosphere15 Hydrologic cycle, part 2 Surface-to-air water movement –Evaporation is responsible for most of the moisture that enters the atmosphere from Earth’s surface. Of the moisture evaporated, more than 84% comes from ocean surfaces. The water evaporated becomes water vapor, and though it stays in atmosphere only briefly (hours to days), it can travel a considerable distance, either vertically or horizontally.

16. Rev. 15 April 2006The Hydrosphere16 Hydrologic cycle, part 3 Air-to-surface water movement –Water vapor will either condense to liquid water or sublimate to ice to form cloud particles. –Clouds drop precipitation (rain, snow, sleet, hail). –Precipitation and evaporation/transpiration balance in time. They do not balance in place. Evaporation exceeds precipitation over oceans. Precipitation exceeds evaporation over lands.

17. Rev. 15 April 2006The Hydrosphere17 Hydrologic cycle, part 4 Movement on and beneath Earth’s surface –Runoff is the flow of water from land to oceans by overland flow, streamflow, and groundwater flow. Runoff is why the oceans do not dry up and continents become flooded despite the imbalance of evaporation and precipitation through space (oceans and continents). Runoff water amounts to 8% of all moisture circulating in global hydrologic cycle.

18. Rev. 15 April 2006The Hydrosphere18 Hydrologic cycle, part 5 Residence times –At any given movement, the atmosphere contains only a few days’ potential precipitation. –The residence time of a molecule of water can be hundreds of thousands of years to only a few minutes.

19. Rev. 15 April 2006The Hydrosphere19

20. Rev. 15 April 2006The Hydrosphere20

21. Rev. 15 April 2006The Hydrosphere21 The oceans, part 1 Knowledge of seas has been very limited until very recently. –Only in about last four decades have we developed technology that allows us to catalog and measure many details of ocean environment. How many oceans? –There is really one ocean divided into four principal parts – the Pacific, Atlantic, Indian, and Arctic. The International Hydrographic Organization has recognized a fifth ocean, the Southern Ocean, south of 60  South latitude.

22. Rev. 15 April 2006The Hydrosphere22

23. Rev. 15 April 2006The Hydrosphere23 The oceans, part 2 How many oceans? (continued) –Most smaller bodies of water are considered portions of oceans. A few are so narrowly connected that they warrant separate consideration, such as the Black Sea, Mediterranean Sea, and Hudson Bay. Characteristics of ocean waters –Significant difference from place to place. –Almost all known minerals found to some extent in seawater, but sodium and chloride most important.

24. Rev. 15 April 2006The Hydrosphere24

25. Rev. 15 April 2006The Hydrosphere25

26. Rev. 15 April 2006The Hydrosphere26 The oceans, part 3 Characteristics of ocean waters (continued) –Salinity is a measure of the concentration of dissolved salts. Geographic distribution of surface salinity varies because of –Varying evaporation rates –Varying fresh water discharge rates. –Temperatures decrease with increasing latitude. –Western sides of oceans are nearly always warmer than eastern margins because of the movements of major ocean currents. –Density varies with temperature, salinity, and depth.

27. Rev. 15 April 2006The Hydrosphere27 The oceans, part 4 Movement of ocean waters –Most motion occurs in waves, currents, and tides. –Movement affects surface waters more than deeper waters. –Disturbances in Earth’s crust under oceans can trigger motion. –Tides cause the greatest vertical movements of ocean waters; they can also cause horizontal movement. Rhythmic oscillations occur about every 6 hours as a result of gravitational attraction of nearby heavenly bodies.

28. Rev. 15 April 2006The Hydrosphere28 The oceans, part 5 Movement of ocean waters (continued) –Currents shift water both horizontally and vertically. Currents are primarily caused by wind flow, but also by contrasts in temperature and salinity. Currents are influenced by size and shape of particular ocean basins, configuration and depth of the sea bottom, and the Coriolis effect. –Waves tend to be just shapes, with very little forward progress.

29. Rev. 15 April 2006The Hydrosphere29 Permanent ice Permanent is the second largest storage reservoir for moisture (still minuscule in comparison to ocean). –The land portion of ice is larger than oceanic ice. –Oceanic ice is made up of fresh water because the ice crystals do not take in the minerals of seawater. –Permafrost is the permanent ground ice of permanently frozen subsoil; it makes up most of the ice beneath the land surface.

30. Rev. 15 April 2006The Hydrosphere30

31. Rev. 15 April 2006The Hydrosphere31

32. Rev. 15 April 2006The Hydrosphere32

33. Rev. 15 April 2006The Hydrosphere33

34. Rev. 15 April 2006The Hydrosphere34

35. Rev. 15 April 2006The Hydrosphere35 Surface water, part 1 Surface water makes up only 0.25% of the world’s total moisture supply. Lakes –A lake is a body of water surrounded by land. –Lakes make up more than 90% of surface water of the continents. –Lake genesis and continued existence occurs through two conditions: Some sort of natural basin having a restricted outlet; Sufficient inflow of water to keep the basin at least partly filled.

36. Rev. 15 April 2006The Hydrosphere36 Surface water, part 2 Lakes (continued) –More than 40% of lake water is salt water. –Lakes are distributed unevenly throughout the world. Lakes are most common where glaciers have been. –The destiny of most lakes is to disappear. –Creation of artificial lakes has had immense ecological and economic consequences, consequences which are not always beneficial.

37. Rev. 15 April 2006The Hydrosphere37

38. Rev. 15 April 2006The Hydrosphere38

39. Rev. 15 April 2006The Hydrosphere39

40. Rev. 15 April 2006The Hydrosphere40

41. Rev. 15 April 2006The Hydrosphere41 Surface water, part 3 Swamps and marshes –Swamps are water bodies with water-tolerant plants, predominantly trees. –Marshes are water bodies with water-tolerant plants, primarily grasses and sedges. Both are flattish surface areas that are submerged in water at least part of the time but shallow enough to permit growth of water- tolerant plants.

42. Rev. 15 April 2006The Hydrosphere42 Surface water, part 4 Rivers and streams –Physical geographers call any flowing water a stream, no matter the size. –A drainage basin is all the land area drained by a river and its tributaries.

43. Rev. 15 April 2006The Hydrosphere43

44. Rev. 15 April 2006The Hydrosphere44

45. Rev. 15 April 2006The Hydrosphere45

46. Rev. 15 April 2006The Hydrosphere46 Underground water, part 1 The total amount of water underground is more than 2.5 times that in lakes and streams. Underground water is more widely distributed than surface water. –It is almost ubiquitous: But the quantity is sometimes limited; But the quality is sometimes poor; Sometimes it is at great depth.

47. Rev. 15 April 2006The Hydrosphere47 Underground water, part 2 All underground water originally comes from above. Two factors affect underground water flow: –Porosity, a measure of the capacity of rock or soil to hold water and air, which is defined as the percentage of total volume of a material that consists of voids. –Permeability, the capacity of soil or rock to transmit water, which is determined by the size of pores and by the degree of interconnectedness. Interstices are a labyrinth of interconnected passageways among the soil particles that comprises nearly half the volume of average soil.

48. Rev. 15 April 2006The Hydrosphere48 Underground water, part 3 An aquifer is where underground water is stored; a permeable subsurface rock layer that can store, transmit, and supply water. An aquiclude is an impermeable rock layer that hinders or prevents water movements. Excludes water because of high density, or as in case of clay, because interstices are many but too small to transmit water.

49. Rev. 15 April 2006The Hydrosphere49 Underground water, part 4 Hydrologic zones are underground layers involved in the general distribution of underground water: –The zone of aeration is the topmost hydrologic zone within the ground, which contains a fluctuating amount of moisture (soil water) in the pore spaces of the soil (or soil and rock). It is a mixture of solids, water, and air; and is of variable depth.

50. Rev. 15 April 2006The Hydrosphere50 Underground water, part 5 Hydrologic zones (continued) –The zone of saturation is the second hydrologic zone below the surface of the ground, whose uppermost boundary is the water table. The pore spaces and cracks in the bedrock and the regolith of this zone are fully saturated. Groundwater is the water found in the zone of saturation. Water table is the top of the zone of saturation within the ground. Where the water table intersects the Earth’s surface, water flows out.

51. Rev. 15 April 2006The Hydrosphere51 Underground water, part 6 Hydrologic zones (continued) –The zone of saturation (continued) A lake, swamp, marsh, or permanent stream is almost always an indication that the water table reaches the surface there. A perched water table occurs when a localized zone of saturation develops above an aquiclude. A cone of depression occurs when water is removed from well faster than underground water can replace it; this lowers the water table, which becomes the approximate shape of an inverted cone in the immediate vicinity of well.

52. Rev. 15 April 2006The Hydrosphere52

53. Rev. 15 April 2006The Hydrosphere53 Underground water, part 7 Hydrologic zones (continued) –The zone of confined water is the third hydrologic zone below the surface of the ground, separated from the zone of saturation by impermeable rock. The zone occurs in many, but not most parts of world. It contains one or more permeable rock layers (aquifers) into which water can infiltrate. If drilled into, confining pressure will force water to rise in the well. Piezometric surface is the elevation to which water will rise under natural confining pressure in a well.

54. Rev. 15 April 2006The Hydrosphere54 Underground water, part 7 Hydrologic zones (continued) –The zone of confined water (continued) An artesian well is created by the free flow that results when a well is drilled from the surface down into a zone of confined water and the confining pressure is sufficient to force the water to the surface without artificial pumping. A subartesian well created by is the free flow that results when a well is drilled from the surface down into a confined aquifer but which requires artificial pumping to raise the water to the surface because the confining pressure forces the water only part way up the well shaft.

55. Rev. 15 April 2006The Hydrosphere55

56. Rev. 15 April 2006The Hydrosphere56

57. Rev. 15 April 2006The Hydrosphere57 Underground water, part 9 Hydrologic zones (continued) –The waterless zone is the lowermost hydrologic zone that generally begins several kilometers or miles beneath the land surface and is characterized by the lack of water in pore spaces due to the great pressure and density of the rock.

58. Rev. 15 April 2006The Hydrosphere58

59. Rev. 15 April 2006The Hydrosphere59 Groundwater mining, part 1 Accumulation of groundwater is tediously slow, but humans can use it up rapidly. –High rates of groundwater use can be likened to mining because a finite resource is being removed with no hope of replenishment. The largest U.S. aquifer, the Ogallala, underlies 585,000 square km (225,000 square mi) of eight states.

60. Rev. 15 April 2006The Hydrosphere60 Groundwater mining, part 2 Ogallala aquifer (continued) –Water accumulated there for some 30,000 years. –Farmers began to tap into it the aquifer in the early 1930s. –The water table is sinking. Used to take 50-foot wells, now some 150 to 250 feet (45 to 75 meters) to access water. Less careful neighbors can harm those farmers who are trying to be very conservative in their water use. If present usage continues in southwestern Kansas, no Ogallala water will exist there after year 2019.

61. Rev. 15 April 2006The Hydrosphere61 Groundwater mining, part 3 Ogallala aquifer (continued) –Water accumulated there for some 30,000 years. –Farmers began to tap into it the aquifer in the early 1930s. –The water table is sinking. Used to take 50-foot wells, now some 150 to 250 feet (45 to 75 meters) to access water. Less careful neighbors can harm those farmers who are trying to be very conservative in their water use. If present usage continues in southwestern Kansas, no Ogallala water will exist there after year 2019.

62. Rev. 15 April 2006The Hydrosphere62 Groundwater mining, part 4 Ogallala aquifer (continued) –It appears to be a matter of when, not if, the finite resource of water from Ogallala will disappear.

63. Rev. 15 April 2006The Hydrosphere63