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Life at the Water’s Edge WHY is this important for reservoirs? John Hains 21 September 2006 Lake Greenwood State Park
Lakes versus Reservoirs • Lakes and Reservoirs Have Different Characteristics, Origins • Processes Occurring in Lakes Also Occur in Reservoirs • There Are Additional Processes in Reservoirs
First: Solar energy drives the entire aquatic ecosystem. The lake’s characteristics are determined by the ways energy is processed, transferred, transformed, and expressed in temperature, weather, and water movement.
Second: The size, shape, geology, topography, vegetation, climate, land-use, and other human activity for the watershed affects the character of the lake.
Third: the internal fate of, and all the processes affecting water and materials in the reservoir, interacting with energy processes and depending on watershed processes - and thusly affecting patterns of stratification, sediment deposition, biological productivity, and water quality
Comparison of Natural Lakes to Reservoirs Characteristic Natural Lakes Reservoirs Distribution Mostly in glaciated regions Located mostly outside region also near rivers , their of glaciation. Mostly in south floodplains and often associated region of U.S. Often in regions with karst regions or of water resource need. coastal plains. Drainage area Smaller ratio of drainage area to Larger ratio of drainage area to lake surface area. to lake surface area. Theoretical Longer, sometimes many years Shorter, often less than 1 year. retention time Longevity Longer Shorter Shoreline Simpler shape, shorter More complex, dendritic, greater SD number
Comparison of Natural Lakes to Reservoirs, cont’d Outflows More stable, lake surface Releases according to fluctuations smaller demand schedules, lake surface fluctuations greater Inflows Often many smaller Often dominated by one or a order streams few major inflows (sometimes other lake outflows). Nutrient This depends on the watershed characteristics loading and the size of the watershed. Water Greater Lesser, especially near clarity headwaters. Note: these last general relationships are less dependable than previous generalizations.
Lake Name Shoreline length (km) Huron 5118 Superior 4796 Kentucky 3830 Michigan 2671 J. Strom Thurmond 1930 Barkley 1616 Hartwell 1548 Erie 1377 Kerr 1287 Ontario 1168 Champlain 945 Lanier 869 Norman 837 Greenwood 320 Tahoe 116 The Reservoir Perspective
5 km 2 km Aerial Views of the lakes Lake Mendota Lake Greenwood Lake Tahoe 20 km
In Conclusion: The fourth factor - shoreline complexity, length, and development – is a factor that can be important for reservoir ecosystems and water quality. And it is the only factor for which individual property owners have direct influence and control.
So the better question for lakeshore management is not “Why?” But rather “Why Not?” In Conclusion: The fourth factor - shoreline complexity, length, and development – is a factor that can be important for reservoir ecosystems and water quality. And it is the only factor for which individual property owners have direct influence and control.