Introducing Physical Geography 6th Edition Chapter 14 PDF

Introducing Physical Geography 6th edition Chapter 14 Freshwater of the Continents Copyright © 2013 John Wiley & Sons, Inc. All rights reserved.  Chapter Outline 1. Freshwater and the Hydrologic Cycle 2. Groundwater 3. Groundwater Us...

Introducing Physical Geography 6th edition Chapter 14 Freshwater of the Continents Copyright © 2013 John Wiley & Sons, Inc. All rights reserved.  Chapter Outline 1. Freshwater and the Hydrologic Cycle 2. Groundwater 3. Groundwater Use and Management © 2013 John Wiley & Sons, Inc. All rights reserved. 4. Surface Water and Streamflow 5. Flooding 6. Lakes 7. Freshwater as a Natural Resource  The Aral Sea The Aral Sea (border of Kazakhstan and Uzbekistan) – reduced in volume as inflow has been diverted to irrigation Formerly the size of Lake Huron Salinity increases Only a small portion © 2013 John Wiley & Sons, Inc. All rights reserved. remains – the Small Sea (2/3rd) 1976 2006 Eye on Global Change  The Aral Sea © 2013 John Wiley & Sons, Inc. All rights reserved. As the Aral Sea shrank, it left behind the hulks of abandoned fishing vessels, now useless without fish. Eye on Global Change  1. Freshwater and the Hydrologic Cycle © 2013 John Wiley & Sons, Inc. All rights reserved. 1. Freshwater and the Hydrologic Cycle  1. Freshwater and the Hydrologic Cycle Paths of Precipitation Land precipitation either runs off or infiltrates into the soil. As runoff, it flows into streams © 2013 John Wiley & Sons, Inc. All rights reserved. As infiltration, it returns to the air through evapotranspiration or percolates downward to become groundwater 1. Freshwater and the Hydrologic Cycle  1. Freshwater and the Hydrologic Cycle Paths of Precipitation Water in the soil- water belt can return to the atmosphere by evaporation or through transpiration by vegetation. A portion of the infiltrating water © 2013 John Wiley & Sons, Inc. All rights reserved. passes through the soil-waterbelt into the ground-water zone. When rain falls rapidly, water runs over the surface as Some precipitation sinks into the overland flow. In periods of natural passageways in soil by heavy, prolonged rain or rapid infiltration. It is held in the soil- snowmelt, overland flow feeds water belt temporarily, where directly to streams. plants can reach it. 1. Freshwater and the Hydrologic Cycle  2. Groundwater Water in the soil-water belt is available to plants © 2013 John Wiley & Sons, Inc. All rights reserved. Water in the unsaturated zone percolates downward The saturated zone of groundwater is where all pores and spaces are filled with water  2. Groundwater © 2013 John Wiley & Sons, Inc. All rights reserved. Steams and rivers carry runoff from the Ponds and lakes are fed by land surface, but in moist climates they groundwater, so their levels are are also fed by groundwater. Fly determined by the water table. fisherman testing the waters near Baxter State Park, Maine Coyhaique, Chile 1. Freshwater and the Hydrologic Cycle  2. Groundwater The Water Table Water table – marks the top of the saturated zone of groundwater. It is highest under hilltops and divides, and it slopes to intersect the surface at lakes, marshes, and streams. Paths of groundwater © 2013 John Wiley & Sons, Inc. All rights reserved. flow – long time for water to flow along the deeper paths, but flow near the surface is faster Most rapid flow is close to the stream, where the arrows converge 2. Groundwater  2. Groundwater Aquifers Aquifers – Sedimentary layers (sand or sandstone) control the storage and movement of groundwater. © 2013 John Wiley & Sons, Inc. All rights reserved. Clean, well-sorted sand (beaches, dunes, or in stream deposits) can hold groundwater equal to about one-third of its bulk volume. Clay and shale beds, by contrast, are relatively impermeable and are known as aquicludes. 2. Groundwater  2. Groundwater Aquifers 1. A porous sandstone layer (aquifer) is sandwiched between two impervious rock layers (aquicludes) 2. Precipitation provides water that saturates the sandstone layer 3. Since the elevation © 2013 John Wiley & Sons, Inc. All rights reserved. of the well that taps the aquifer is below that of the range of hills feeding the aquifer, pressure forces water to rise in the well (artesian well). 2. Groundwater  2. Groundwater Limestone Solution by Groundwater Carbonic acid action dissolves limestone, producing caverns. Cavern collapse creates sinkholes and a karst landscape Carbonic acid – a weak acid produced from carbon dioxide © 2013 John Wiley & Sons, Inc. All rights reserved. dissolved in water – slowly erodes limestone at the surface in moist climates Similarly, limestone below the surface can be dissolved by groundwater slowly flowing in the saturated zone, forming deep underground limestone caverns 2. Groundwater  2. Groundwater Limestone Solution by Groundwater © 2013 John Wiley & Sons, Inc. All rights reserved. Stage 1 Carbonic acid action is concentrated in the saturated zone just below the water table. Limestone dissolves at the top of the groundwater zone, creating tortuous tubes and tunnels, great open chambers, and tall chimneys below the ground. Subterranean streams can flow in the lowermost tunnels. 2. Groundwater  2. Groundwater Limestone Solution by Groundwater Travertine forms: stalactites (hanging rods) stalagmites (upward- © 2013 John Wiley & Sons, Inc. All rights reserved. pointing rods) columns drip curtains Stage 2 Stream has deepened its valley, water table level drops. Previously formed cavern system now lies in the unsaturated zone. Water flows through caverns, depositing travertine on exposed rock surfaces in the caverns. 2. Groundwater  2. Groundwater Limestone Solution by Groundwater © 2013 John Wiley & Sons, Inc. All rights reserved. White limestone is exposed in the nearly vertical sides of these towers. Near Guilin (Kweilin), Guanxi Province, southern China. 2. Groundwater  2. Groundwater Limestone Solution by Groundwater © 2013 John Wiley & Sons, Inc. All rights reserved. Over time, rainwater dissolves Eventually, the caverns collapse, limestone, producing caverns leaving open, flat-floored valleys. and sinkholes. In warm, humid Surface streams flow on shale beds climates, solution of pure beneath the limestone. Some parts of limestone can form towers. the flat-floored valleys can be cultivated. 2. Groundwater 2. Groundwater 2. Groundwater © 2013 John Wiley & Sons, Inc. All rights reserved.  3. Groundwater Use and Management Groundwater Withdrawal Wells draw down the water table at a point, creating a cone of depression As many wells exploit an aquifer, their cones of depression merge to create a general lowering of the water table © 2013 John Wiley & Sons, Inc. All rights reserved. Old-fashioned dug well supplies water for household needs in Uttar Pradesh, India Well is lined with bricks, and groundwater seeps in to fill the well 3. Groundwater and Use Management  3. Groundwater Use and Management Groundwater Withdrawal Wells draw down the water table at a point, creating a cone of depression As the well draws water, the © 2013 John Wiley & Sons, Inc. All rights reserved. water table is depressed in a cone shape centered on the well This cone of depression may extend out as far as 15 km (9.3 mi) or more from a well where heavy pumping is continued 3. Groundwater and Use Management  3. Groundwater Use and Management Subsidence Subsidence: the sinking of the ground surface due to excessive groundwater withdrawal © 2013 John Wiley & Sons, Inc. All rights reserved. Land subsidence has subjected Venice to episodes of flooding by the Adriatic Sea. Here, high water has swamped the Piazza San Marco and an outdoor café. 3. Groundwater and Use Management  3. Groundwater Use and Management Pollution of Groundwater Sanitary landfills can release pollutants and toxic compounds that infiltrate to the water table, causing ground water contamination that renders adjacent well © 2013 John Wiley & Sons, Inc. All rights reserved. waters unfit for consumption Polluted water, leached from a waste disposal site, moves toward a supply well (right) and a stream (left) 3. Groundwater and Use Management  4. Surface Water and Streamflow Overland Flow Runoff flowing down the land slopes in sheets is called overland flow Several forms: Smooth soil or rock surface: flow as a continuous thin film, called sheet flow Rough or pitted ground: © 2013 John Wiley & Sons, Inc. All rights reserved. overland flow in a series of tiny rivulets Grass-covered slope: overland flow is divided into countless tiny threads of water, passing around the stems 4. Surface Water and Streamflow  4. Surface Water and Streamflow Drainage System A drainage basin, or watershed, consists of a branched network © 2013 John Wiley & Sons, Inc. All rights reserved. of stream channels and adjacent slopes that feed the channels It is bounded by a drainage divide 4. Surface Water and Streamflow  4. Surface Water and Streamflow Stream Channels and Discharge Stream – long, narrow body of water flowing through a channel and moving to lower levels under the force of gravity Stream channel – narrow trough, © 2013 John Wiley & Sons, Inc. All rights reserved. shaped by the forces of flowing water The rate of water flow in a stream is called discharge It is the product of the mean velocity and the cross-sectional area Friction slows flowing water near the banks and bed of the stream, so the velocity of flow is greatest in the middle and at the top of the stream 4. Surface Water and Streamflow  4. Surface Water and Streamflow Stream Channels and Discharge Average velocity (V), cross-sectional area (A) and slope (S) change between © 2013 John Wiley & Sons, Inc. All rights reserved. pools and rapids Cross-sectional area and average velocity of a stream can change within a short distance Volume of water per unit time passing through a cross section of the stream at that location (stream discharge, Q) remains constant 4. Surface Water and Streamflow  4. Surface Water and Streamflow Stream Channels and Discharge Schematic map shows the relative magnitude of the discharge of U.S. rivers © 2013 John Wiley & Sons, Inc. All rights reserved. Width of the river is proportional to mean annual discharge 4. Surface Water and Streamflow  4. Surface Water and Streamflow Stream Channels and Discharge A hydrograph plots streamflow with time. Peaks in the hydrograph occur after rainfall events. Between rains, streamflow falls to base flow, which is supplied by groundwater seepage. © 2013 John Wiley & Sons, Inc. All rights reserved. 4. Surface Water and Streamflow  5. Flooding Floodplain A flood occurs when a river rises over its banks and covers adjacent land, which is called the floodplain The height of the river at that time and place is called the flood stage © 2013 John Wiley & Sons, Inc. All rights reserved. Floodplain: a flat area bordering the channel on one or both sides that fills with water during a flood 5. Flooding  5. Flooding Urbanization and Streamflow The growth of cities and suburbs affects the flow of small streams in two ways: 1. It is more difficult for water to infiltrate the ground, which is more widely covered by buildings, © 2013 John Wiley & Sons, Inc. All rights reserved. driveways, walks, pavements, and parking lots 2. The introduction of storm sewers, systems of large underground pipes designed to Impervious surfaces like this street in quickly transport storm Bangkok increase runoff and hasten the runoff from paved areas directly to flow of water into streams and rivers stream channels for discharge draining urban environments 5. Flooding 5. Flooding 5. Flooding © 2013 John Wiley & Sons, Inc. All rights reserved.  6. Lakes Lake – a body of standing water with a surface that is exposed to the atmosphere and does not have an appreciable gradient. (Ponds, marshes, and swamps with standing water included in definition of a lake) © 2013 John Wiley & Sons, Inc. All rights reserved. Lakes are usually larger and deeper The shallow waters of this pond in than ponds. Many lakes are artificial, Nicolet National Forest, Wisconsin, dammed to provide water supplies or support an almost continuous cover hydroelectric power. of grasses and sedges. 6. Lakes  6. Lakes Lakes serve as vital reservoirs of fresh water on the land. The are formed in many different ways but are generally short-lived over geologic time. © 2013 John Wiley & Sons, Inc. All rights reserved. Water level of freshwater ponds in sandy glacial deposits ponds is close to the level of the water table 6. Lakes  6. Lakes The Great Lakes The Great Lakes are a great North American water resource, although they have suffered from water pollution. Great Lakes – vast water resource lying astride the boundary between © 2013 John Wiley & Sons, Inc. All rights reserved. Canada and the United States - Superior - Huron - Michigan - Erie - Ontario 6. Lakes  6. Lakes The Great Lakes © 2013 John Wiley & Sons, Inc. All rights reserved. Volumes, elevations, and depths of the five Great Lakes 6. Lakes  6. Lakes Saline Lakes and Salt Flats Arid regions – Lakes without surface outlet Average rate of evaporation balances the average rate of stream inflow When the rate of inflow increases, the lake level rises and the © 2013 John Wiley & Sons, Inc. All rights reserved. lake’s surface area increases, allowing more evaporation and striking a new balance If region becomes more arid, reducing input and increasing evaporation, the water level will fall to a lower level Salinization and waterlogging – undesirable side effects of continued irrigation 6. Lakes  6. Lakes Saline Lakes and Salt Flats © 2013 John Wiley & Sons, Inc. All rights reserved. Swimmers in the Dead Sea float easily on the dense, salty water 6. Lakes  6. Lakes Saline Lakes and Salt Flats © 2013 John Wiley & Sons, Inc. All rights reserved. Salt flats – dry lake bottoms covered with mineral salts and sediments Bonneville Salt Flats has a uniform and smooth surface, used as a speedway for high-speed race cars 6. Lakes  6. Lakes Desert Irrigation Desert irrigation – ancient Egypt and Mesopotamia relied on irrigation with supplies of water from nondesert sources Exotic rivers – rivers that cross the desert but derive their flow from regions having a water surplus © 2013 John Wiley & Sons, Inc. All rights reserved. Salinization and waterlogging are undesirable side effects of long-term irrigation Arid regions watered by exotic rivers are most affected 6. Lakes  7. Freshwater as a Natural Resource Water Access and Supply Human society is heavily dependent on fresh surface water for irrigation, drinking water, and industrial usage Freshwater is a limited resource © 2013 John Wiley & Sons, Inc. All rights reserved. Industry: In industrial economies, significant portions of water use support industry, such Power: Water is valued as a source of hydroelectric as the iron and steel manufacturing along the power. Here, massive water pipes funnel water from Calumet River in Chicago. Industrial water the Euphrates River to turbines in Turkey’s Ataturk waste can contaminate water sources or Dam, the centerpiece of a controversial plan to damage ecosystems. irrigate southeastern Turkey.  7. Freshwater as a Natural Resource Water Access and Supply © 2013 John Wiley & Sons, Inc. All rights reserved. Drinking Water: In arid and poorly developed regions, large numbers of inhabitants lack easy access to clean drinking water. As many as Agriculture: In most of the world’s watersheds, 4500 children die each day from lack of safe agriculture is the major consumer of freshwater. drinking water, according to UNICEF. In some When diverted from large rivers, surface water parts of the world, such as Anuradhapura, Sri provides irrigation water for agricultural purposes Lanka, carrying water from a well or spring is a large and small, as with these Vietnamese farmers daily chore. using foot power to raise water from a canal.  7. Freshwater as a Natural Resource Pollution of Surface Water Water pollutants include various types of common ions and salts, as well as heavy metals, organic compounds, and acids. Excessive plant nutrients in runoff feeding © 2013 John Wiley & Sons, Inc. All rights reserved. lakes can lead to eutrophication. Acid mine drainage is a major problem in areas of strip mining. 7. Freshwater as a Natural Resource  7. Freshwater as a Natural Resource Pollution of Surface Water Sources of water pollutants: Toxic metals and organic compounds from industrial plants Discharge untreated or partly treated sewage Fertilizers and livestock wastes Mining and processing of mineral deposits © 2013 John Wiley & Sons, Inc. All rights reserved. Radioactive substances released from nuclear power and processing plants Eutrophication – phosphate and nitrates encourage algae and other aquatic plants to grow. Process is known as “aging” of a lake. Thermal pollution – heat as a byproduct of fuel combustion or nuclear generation and steam discharged into the environment. 7. Freshwater as a Natural Resource