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Water Quality 



The natural quality of water in the Nation's streams 

 and lakes is, in large part, a reflection of the charac- 

 teristics of the land and vegetation from which the 

 water flows. Because of the natural variation in land 

 and vegetation, the natural quality of water in streams 

 and lakes is neither uniform nor static. Water is con- 

 stantly moving, even in lakes and reservoirs; as it 

 moves, its quality changes. It is influenced by natural 

 features including geological features, soil, vegetation, 

 natural landslides, and wildfire. 



The natural quality of water is also affected by the 

 actions of people. These actions include road con- 

 struction, urban development, farming, mining, tim- 

 ber harvesting, livestock grazing, and dumping of 

 municipal and industrial wastes. Acid precipitation, 

 which occurs when precipitation falls through air 

 containing heavy concentrations of sulfur, also affects 

 water quality, especially near heavily industrialized 

 areas. 



Water is often used and reused several times and 

 for many purposes during its journey to the sea. 

 Quality can be either improved or degraded as it is 

 used and returned to the stream. Because it is ever- 

 moving and ever-changing, water quality and quantity 

 are difficult to inventory or measure. 



It is important to realize that water quality deter- 

 mines the usability of water and that quality can be 

 good or bad, depending on the specific uses man 

 wishes to make of it. For example, a clear alpine lake 

 may be excellent for esthetic enjoyment and trout 

 fishing, but very poor for swimming since the water 

 temperature rarely exceeds 10 degrees centigrade. 

 Another example would be when the natural water 

 quality is ideal for swimming and for fish, wildlife, 

 and livestock, but is unsatisfactory for industrial 

 use because of the content of total dissolved solids. 



To show the relationship of water quality to its 

 natural environment, relatively undisturbed forest and 

 range land watersheds with available water quality 

 data were selected in each division, province, or sec- 

 tion as described by Bailey.'' ^ Bailey's hierarchical 

 system for land classification (ecoregions) begins with 

 the largest, broadest definition as a domain, and 

 proceeds downward in size and in specificity through 

 division and province to section, the smallest and 

 most discrete unit. Each section describes a more or 

 less continuous geographical area and is characterized 

 by distinctive fauna, climate, landform (including 

 drainage pattern), soil, and vegetation that distin- 



- sSSr 



ffl n o 2 

 5 S D. O 



'Bailey, Robert. Ecoregions of the United States (map). U.S. 

 Department of Agriculture, Forest Service, Ogden, Utah. 1976. 



* Bailey, Robert. Description of the ecoregions of the United 

 States. U.S. Department of Agriculture, Forest Service, Ogden, 

 Utah. 



301 



