Life at the Water’s Edge

WHY is this important for reservoirs?

John Hains21 September 2006

Lake Greenwood State Park

Lakes versus Reservoirs

I. Lakes and Reservoirs Have Different Characteristics, Origins

II. Processes Occurring in Lakes Also Occur in Reservoirs

III. 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 regionalso near rivers , their of glaciation. Mostly in southfloodplains 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

Lake Surface Area

(sq. km)

Shoreline

(km)

Shoreline

Development

Watershed

Area (sq. km)

Watershed/

Surface Area

Huron 59600 6157 7.11 134100 2.25

Superior 82100 4796 4.72 128076 1.56

Kentucky 648 3830 42.44 105151 162.27

Michigan 57800 2671 3.13 117912 2.04

J. Strom Thurmond

283 1930 32.36 15961 56.40

Barkley 378 1616 23.45 45579 120.58

Hartwell 227 1548 28.98 5405 23.81

Erie 25700 1377 2.42 78128 3.04

Greenwood 46 320 13.31 1891 41.12

Tahoe 495 114 1.45 812 1.60

Mendota 40 35.2 1.57 602 15.11

Lake Surface Area

(sq. km)

Shoreline

(km)

Shoreline

Development

Watershed

Area (sq. km)

Watershed/

Surface Area

Greenwood 46 320 13.31 1891 41.12

Tahoe 495 114 1.45 812 1.60

Mendota 40 35.2 1.57 602 15.11

20 km

Lake Tahoe 2 km

5 km

Lake Mendota

Lake Greenwood

Aerial Views of the lakes

Lake Surface Area

(sq. km)

Shoreline

(km)

Shoreline

Development

Watershed

Area (sq. km)

Watershed/

Surface Area

Greenwood 46 320 13.31 1891 41.12

Tahoe 495 114 1.45 812 1.60

Mendota 40 35.2 1.57 602 15.11

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.

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?”