Ellen E. Wohl
- Published in print:
- 2004
- Published Online:
- October 2013
- ISBN:
- 9780300103328
- eISBN:
- 9780300127461
- Item type:
- chapter
- Publisher:
- Yale University Press
- DOI:
- 10.12987/yale/9780300103328.003.0007
- Subject:
- Environmental Science, Environmental Studies
This chapter discusses the endangered rivers of the United States, and the actions required to save them. It reveals that rivers of the Lower Mississippi region were first heavily impacted by ...
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This chapter discusses the endangered rivers of the United States, and the actions required to save them. It reveals that rivers of the Lower Mississippi region were first heavily impacted by dramatically increased sediment yields from lands being cleared of natural vegetation for growing crops. River response to sedimentation prompted humans to undertake widespread channelization, construction of levees, clearing of logjams and naturally occurring wood, and destruction of riverside and floodplain habitats. Rivers of the Central region have been most altered by flow regulation and changes in sediment supply associated with dams, diversions, and channelization, and by contamination from agricultural runoff. The chapter discusses how the big rivers of the Southwestern Canyon region were most heavily affected by the construction of numerous large dams and the removal of water for off-stream agricultural and municipal uses during the twentieth century.Less
This chapter discusses the endangered rivers of the United States, and the actions required to save them. It reveals that rivers of the Lower Mississippi region were first heavily impacted by dramatically increased sediment yields from lands being cleared of natural vegetation for growing crops. River response to sedimentation prompted humans to undertake widespread channelization, construction of levees, clearing of logjams and naturally occurring wood, and destruction of riverside and floodplain habitats. Rivers of the Central region have been most altered by flow regulation and changes in sediment supply associated with dams, diversions, and channelization, and by contamination from agricultural runoff. The chapter discusses how the big rivers of the Southwestern Canyon region were most heavily affected by the construction of numerous large dams and the removal of water for off-stream agricultural and municipal uses during the twentieth century.
Ellen Wohl
- Published in print:
- 2004
- Published Online:
- October 2013
- ISBN:
- 9780300103328
- eISBN:
- 9780300127461
- Item type:
- book
- Publisher:
- Yale University Press
- DOI:
- 10.12987/yale/9780300103328.001.0001
- Subject:
- Environmental Science, Environmental Studies
This book focuses on how rivers function, how those functions have changed through time, and the role of humans in those changes. A river continually responds to changes in its environment and is ...
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This book focuses on how rivers function, how those functions have changed through time, and the role of humans in those changes. A river continually responds to changes in its environment and is never static. The type of river response depends on the magnitude and persistence of changes in water and sediment entering the river. The movements of water and sediment within a sand-bed channel adjust readily over a period of minutes to hours. The book discusses rivers of the Northeast and East-Central region of the United States, which drain east to the Atlantic Ocean. The single largest drainage basin in this region is the St. Lawrence, which delivers an average of 65,000 billion gallons of water to the ocean each year. The book examines the river systems in America, explains how the earliest human inhabitants reached America and modified the physical and biological environments of the rivers, and reveals that sedentary agricultural communities first appeared in the archeological record of North America more than 2,000 years ago. As with agricultural peoples elsewhere in the world, these first farmers affected rivers more than their hunter-gatherer predecessors. The book discusses the impact of industrialization on the health of rivers in United States, also focusing on the restoration and rehabilitation of rivers.Less
This book focuses on how rivers function, how those functions have changed through time, and the role of humans in those changes. A river continually responds to changes in its environment and is never static. The type of river response depends on the magnitude and persistence of changes in water and sediment entering the river. The movements of water and sediment within a sand-bed channel adjust readily over a period of minutes to hours. The book discusses rivers of the Northeast and East-Central region of the United States, which drain east to the Atlantic Ocean. The single largest drainage basin in this region is the St. Lawrence, which delivers an average of 65,000 billion gallons of water to the ocean each year. The book examines the river systems in America, explains how the earliest human inhabitants reached America and modified the physical and biological environments of the rivers, and reveals that sedentary agricultural communities first appeared in the archeological record of North America more than 2,000 years ago. As with agricultural peoples elsewhere in the world, these first farmers affected rivers more than their hunter-gatherer predecessors. The book discusses the impact of industrialization on the health of rivers in United States, also focusing on the restoration and rehabilitation of rivers.
J. H. Wang
- Published in print:
- 1997
- Published Online:
- November 2020
- ISBN:
- 9780195097450
- eISBN:
- 9780197560846
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780195097450.003.0015
- Subject:
- Earth Sciences and Geography, Soil Science
The properties of hydrogen and aluminum ions have been examined in Chapters 10 and 11. These two ion species are ions that directly induce the acid reaction in soils. ...
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The properties of hydrogen and aluminum ions have been examined in Chapters 10 and 11. These two ion species are ions that directly induce the acid reaction in soils. In soils devoid of soluble salts, the content of cations is constant and the negative surface charges are saturated by, besides hydrogen and aluminum ions, alkali metal and alkaline earth metal ions. These ions are called base ions. The acidity of a soil is determined chiefly by the ratio of the quantity of hydrogen and aluminum ions to that of base ions. Among these base ions, calcium ions occupy the most important position, because they generally account for 65-80% of the total amount of base ions in variable charge soils. Therefore, calcium is an ion species closely related to the acidity of soils. In addition to the parameter pH that directly reflects the concentration of hydrogen ions, one other desirable way is to find a parameter that can reflect the ratio of the hydrogen ions to the calcium ions. This parameter is the lime potential. Since the introduction of the concept of lime potential 40 years ago, little practical application has been made in soil science, although some further theoretical considerations were advanced in the 1950s and the 1960s. Actually, as shall be seen in this chapter, for strongly acid soils, such as variable charge soils, because the quantity of hydrogen ions is too high and at the same time the quantity of calcium ions is too low, lime potential that can reflect the relative ratio of these two ion species is of significance not only in theory but also in practice. The mathematical expression of lime potential is pH-0.5pCa. Lime potential is a simple function of the chemical potential of calcium hydroxide, lime. Hence it may be called lime potential. The physical meaning of pH-0.5pCa can be derived as follows.
Less
The properties of hydrogen and aluminum ions have been examined in Chapters 10 and 11. These two ion species are ions that directly induce the acid reaction in soils. In soils devoid of soluble salts, the content of cations is constant and the negative surface charges are saturated by, besides hydrogen and aluminum ions, alkali metal and alkaline earth metal ions. These ions are called base ions. The acidity of a soil is determined chiefly by the ratio of the quantity of hydrogen and aluminum ions to that of base ions. Among these base ions, calcium ions occupy the most important position, because they generally account for 65-80% of the total amount of base ions in variable charge soils. Therefore, calcium is an ion species closely related to the acidity of soils. In addition to the parameter pH that directly reflects the concentration of hydrogen ions, one other desirable way is to find a parameter that can reflect the ratio of the hydrogen ions to the calcium ions. This parameter is the lime potential. Since the introduction of the concept of lime potential 40 years ago, little practical application has been made in soil science, although some further theoretical considerations were advanced in the 1950s and the 1960s. Actually, as shall be seen in this chapter, for strongly acid soils, such as variable charge soils, because the quantity of hydrogen ions is too high and at the same time the quantity of calcium ions is too low, lime potential that can reflect the relative ratio of these two ion species is of significance not only in theory but also in practice. The mathematical expression of lime potential is pH-0.5pCa. Lime potential is a simple function of the chemical potential of calcium hydroxide, lime. Hence it may be called lime potential. The physical meaning of pH-0.5pCa can be derived as follows.
