Environmental Engineering Reference
In-Depth Information
1
The Wate rshedApproach
1.1 Introduction
John Wesley Powell, scientist, explorer, and an early director of the U.S. Geological Survey,
put it best when he said that a watershed is
… that area of land, a bounded hydrologic system, within which all living things are
inextricably linked by their common water course and where, as humans settled, simple
logic demanded that they become part of a community.
Powell spoke these words in the late 1800s. Since then, population has increased dramati-
cally and more people have become part of the watershed community. This increase in
population within a finite hydrologic system has created new and increasingly complex
human-environmental interactions.
Watersheds come in all shapes and sizes. They cross county, state, and national boundar-
ies. In the continental United States, there are 2110 watersheds; including Hawaii, Alaska,
and Puerto Rico, there are 2267 watersheds. Many of these watersheds contain homog-
enous land uses and land cover, such as agriculture, forest, or mountains. Others are more
densely populated and consist of political units each pursuing their own self-interest,
making it even more difficult to achieve consensus on how to solve a particular problem.
A watershed also contains a great diversity of people. Among this diversity are people
who live a rural lifestyle, suburbanites, and those living in an urban setting.
Urban watersheds are unique in the sense they typically contain a full palette of land uses
and land cover types. Headwater regions of urban streams may contain endangered species
of fish and local farms, while older manufacturing sites often sit idle within the original
urban core. Many of the fundamental processes that contribute to the occurrence and dis-
tribution of contamination in the urban environment such as the movement of water and
the location of industry are closely linked to drainage patterns. For this reason, an interdis-
ciplinary scientific watershed approach is required to account for their full natural variability
and the resulting implications for society. The watershed approach is thus a framework
that uses science from various disciplines to characterize the physical and social processes
occurring within a watershed in order to help solve some of its environmental problems.
1.2 Historical Transformation of Urbanized
Watersheds by Industrial Development
In the process of urban development, both technology and environment have profoundly
influenced the relationships between site and geographic situation. Early settlements in
North America tended to be dependent on water for power, transportation, and supply,
 
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