Watershed

W. Stumm andj. J. Morgan, Mquatic Chemistry Mn Introduction Emphasising Chemical Equilibria in Natural Watersh]Mm. Wiley Sons, Inc., New York, 1970, pp. 474, 502-503. 

The Greenman decision was a watershed, and privity-free strict HabiUty in tort swept the country as a tidal wave. In 1965, the American Law Institute embraced the concept in Section 402A, and thousands of decisions cited to the Restatement. Within a decade the decision became the majority rule in the United States in the 1990s all but a tiny minority of states ascribe to it. 

Consider a lake with a smaU watershed in a forest ecosystem. The forest and vegetation can be considered as an acid concentrator. SO2, NO2, and acid aerosol are deposited on vegetation surfaces during dry periods and rainfalls they are washed to the soil floor by low-pH rainwater. Much of the acidity is neutralized by dissolving and mobilizing minerals in the soil. Aluminum, calcium, magnesium, sodium, and potassium are leached from the soil into surface waters. The ability of soils to tolerate acidic deposition is very dependent on the alkalinity of the soil. The soil structure in the... 

Assists in modeling a watershed and creating the inputs to HEC-1 for hydrologic simulations. 

The amount of hardness present in natural surface and groundwaters depends to a large extent on the action of dissolved carbon dioxide in rainwater on the watershed s geological formations (such as limestone, dolomite, gypsum, or magnesite). The dissolved hardness levels remain relatively low because of the sparingly soluble nature of the salts formed. Typically, MU water sources initially contain anywhere from 5... 

Figure 6. Watershed Flow Chart Showing Key Hydrological and Biochemical Processes that Affect Acidification, adapted from reference 52.

The nature of human impacts on the Great Lakes relates closely to historical development and land use in the basin which, in turn, relate closely to the geology and physiography of the watershed. The southern part of the basin consists largely of Palaeozoic sedimentary rocks. Land use consists primarily of intense... 

Barnes, R.S. Schell, W.R. Physical Transport of Trace Metals in the Lake Washington Watershed. In Cycling and Control of Metals, Proc. of an... 

In 1968, reports from Sweden, subsequently confirmed in other industrial countries, noted that shallow lakes with low concentrations of divalent cations were becoming more acidic with consequent decreases in aquatic plants and animals. In severely affected lakes and ponds, only acidophilic algae survived. Increased acidity and the runoff of solubilized aluminum and other metal ions from surrounding watersheds are now known to be primarily responsible for formation of these almost sterile bodies of water. 

DeByle, N.V. Packer, P.E. National Symposium on Watersheds in Transition. American Water Resources Association Bethesda, MD, 1976, pp 296-307. 

Many hydrologic reservoirs can be further subdivided into smaller reservoirs, each with a characteristic turnover time. For example, water resides in the Pacific Ocean longer than in the Atlantic, and the oceans surface waters cycle much more quickly than the deep ocean. Similarly, groundwater near the surface is much more active than deep reservoirs, which may cycle over thousands or millions of years, and water frozen in the soil as permafrost. Typical range in turnover times for hydrospheric reservoirs on a hillslope scale (10-10 m) are shown in Table 6-4 (estimates from Falkenmark and Chapman, 1989). Depths are estimated as typical volume averaged over the watershed area. 

Longer turnovers associated with large watershed areas. 

Because it depends on a number of conditions that are themselves inherently variable, runoff tends to vary even more than precipitation, particularly over time. Seasonal runoff patterns depend largely on latitude and altitude of the watershed, due to the importance of snowmelt in runoff peaks. In high-latitude basins or those with significant high-altitude contribut-... 

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