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1. Water and Life
Pages 17-31

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From page 17...
... Because of water's special character, oceans and large lakes fluctuate little in temperature, and the heat-sensitive proteins within plant and animal cells are insulated by their aqueous baths. · Global heat exchanger When changing among its liquid, vapor, and solid states (at constant temperature)
From page 18...
... ROUND AND ROUND AND ROUND IT GOES The pathway of water as it moves in its various phases through the atmosphere, to the earth, over and through the land, to the ocean, and back to the atmosphere is known as the hydrologic cycle (Figure 1.1~. 1 Precipitation on land Moisture over land Evaporation from land Precipitation on ocean Infiltration ~`,` Moisture Water ~ table Go Evaporation and evapotranspiration KIWI lUWdlUl IIUW _ Evaporation from ocean Surface outflow Groundwater outflow FIGURE 1.1 Elements of the hydrologic cycle.
From page 19...
... Prime examples are plants, which regulate the rate at which a land surface returns water vapor to the atmosphere, and humans, who alter nearly all aspects of water on land. Such interactions are not limited to living things, however, if we consider longer time scales.
From page 20...
... Then, as the waters receded, shrinking back to the main channel by October, they left behind a soil-building layer of silt, and a great agricultural potential. "Egypt," Herodotus said some 2,400 years ago, "is the gift of the river." The Egyptians used their hydraulic engineering skills to make the most of this already beneficial relationship: they built simple canals, dikes, and reservoirs to help manage the water and increase crop production.
From page 21...
... These fluctuations influence both the amount and distribution of precipitation. A culture tied closely to a particular climate will be in jeopardy when its water supplies are reduced.
From page 22...
... 22 OPPORTUNITIES IN THE HYDROLOGIC SCIENCES ships to land transport or river craft. For similar reasons cities are often found at the junctions of mountain and plain.
From page 23...
... WATER AND LIFE 23 Floods A flood is an overflowing of water onto land not usually submerged. For scientific purposes the size of a flood is usually measured in terms of the maximum flow rate (cubic meters per second)
From page 24...
... The Hwang Ho is also called the Mother of China because of the fresh topsoil the floods bring to the land. The major scientific challenge with respect to floods here lies with improved short-range forecasting, but the principal hope for reduction of the losses lies with public policy that regulates development in the floodplain.
From page 26...
... We now realize that many of the waste materials thought to be "out of sight, out of mind" when disposed of within the earth are dissolved in ground water and hence reenter the hydrologic cycle as these waters rejoin the rivers. Regulatory action to control this practice is in its infancy, and cleanup of past damage is a difficult and costly task.
From page 27...
... The Army Corps of Engineers, the Bureau of Reclamation, the Soil Conservation Service, and other agencies engaged in a period of intense water resources management in response to various pieces of legislation intended to control floods, irrigate 17 western states, conserve soil and water, and provide navigable streams, hydroelectric power, water supplies, recreation, drainage, and other functions. The accomplishments during this extremely active period of development are impressive indeed.
From page 28...
... Continued progress in providing safe drinking water will allow countries to focus on other water issues, such as irrigation for sustainable agriculture, and environmental problems, such as soil erosion, deforestation, and hazardous waste management. Contemoorarv Water Resources Management Problems Efforts to provide for the water-related needs of the world's populations have been impressive, but population growth and the changing demands of increasingly sophisticated societies have put unparalleled pressures on water resources.
From page 30...
... Nonpoint pollution includes fertilizer and sediment runoff from agricultural fields, acid deposition from the atmosphere, detergents, oils, metals and fecal material carried in urban storm sewers, and other substances that cannot be identified as coming from a single source. This type of pollution can be particularly difficult to identify, let alone prevent, as is clearly the case at the Chesapeake Bay in the eastern United States.
From page 31...
... The benefits society will ultimately receive from a thorough scientific understanding of water behavior are many. Advances in the areas of irrigation, drinking water and ground water supplies, improved recreational areas and wildlife habitat, and flood and drought forecasting and planning are only a few examples.


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