North Temperate Lakes

NTL researchers developed the “lake landscape position” concept to explain spatial variability in water chemistry and community composition that results from a shifting balance of groundwater, surface water, and precipitation inputs to adjacent lakes.

NTL developed the concept of “lake landscape position” – how a lake’s location within the larger landscape provides a basis for understanding lake characteristics and dynamics.  Lakes can receive water from precipitation, surface runoff (streams and rivers) and groundwater.  In general, lakes higher in the landscape (i.e., at greater elevations) receive a larger percentage of their incoming water from precipitation than lakes lower in the landscape, which have substantial stream and groundwater inputs in addition to precipitation. This shifting balance of water sources to lakes along an elevation gradient results in predictable changes in physical, chemical, biological, and social aspects of these systems.

Lakes high in the landscape tend to be smaller, clearer, more chemically dilute, more sensitive to acidification, less biologically diverse, and less used by humans for motorized recreation than lakes lower in the landscape.  And because of their dependence on precipitation, lakes high in the landscape are more sensitive to drought, as their lake levels can fluctuate up to ten times more that lakes lower in the landscape.  This overarching framework relating a lake’s hydrologic setting to its ecological and socio-economic attributes has allowed NTL scientists to gain new understanding of land-water interactions.  For example we have a better understanding of why one lake may experience dramatic changes in water chemistry during dry years while a neighboring lake only a mile away may experience little or no change even though they are in the same geological, climatic and cultural setting.

Understanding how a lake’s position in the landscape influences its characteristics and dynamics is a powerful tool for forecasting how and why lakes will respond differentially to changes in land use and climate or to establishment of aquatic invasive species and other disturbances.  This understanding frees policy makers from having to use “one size fits all” management policies for lakes.

Further reading:

Kratz, T. K., K. E. Webster, J. L. Riera, D. B. Lewis, and A. I. Pollard.  2006.  Making sense of the landscape: geomorphic legacies and the landscape position of lakes.  Pages 49-66 in Magnuson, J. J., T. K. Kratz, and B. J. Benson (eds.) Long-Term Dynamics of Lakes in the Landscape: Long-Term Ecological Research on North Temperate Lakes. Oxford University Press, New York. 400pp.

Riera, J. L., J. J. Magnuson, T. K. Kratz, and K. E. Webster. 2000.  A geomorphic template for the analysis of lake districts applied to the Northern Highland Lake District, Wisconsin, USA.  Freshwater Biology 43:301-318.

Webster, K. E., T. K. Kratz, C. J. Bowser, J. J. Magnuson, and W. J. Rose.  1996.  The influence of landscape position on lake chemical responses to drought in northern Wisconsin, USA.  Limnology and Oceanography 41:977-984.