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The Effect of Light Extinction on Thermal Stratification in Reservoirs and Lakes
Author(s) -
Hocking G. C.,
Straškraba M.
Publication year - 1999
Publication title -
international review of hydrobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 1434-2944
DOI - 10.1002/iroh.199900046
Subject(s) - water column , stratification (seeds) , thermal stratification , extinction (optical mineralogy) , attenuation , environmental science , dissipation , mechanics , atmospheric sciences , geology , physics , mineralogy , oceanography , optics , thermodynamics , turbulence , biology , seed dormancy , botany , germination , dormancy
Abstract An examination is made of the effect of light attenuation in the water column on the hydrodynamics, and in particular on temperature stratification in reservoirs. Numerical experiments are described which examine the differences in light profile in the water column when the spectral character of the incident radiation and light penetration is and is not taken into account. It was found that the exponential character of light penetration remains but the exponent may be increased by up to 20% in clear waterbodies and less in waterbodies with higher extinction values when I 0 (λ) and K d (λ) are incorporated. The error may be higher when the spectral character of the extinction is due to colored organics rather than phytoplankton. The numerical, one dimensional hydrodynamic model DYRESM is used to isolate and examine the influence of changing the light attenuation in the water column in a reservoir, and on its hydrodynamics, when keeping other conditions unchanged. Not surprisingly, the simulations show that when the extinction rate increases, mixing depth decreases markedly, and although the same energy enters the water column, surface temperatures increase slightly while deep temperatures decrease. Some other surprising effects were found and are described. The results presented and comparison of the model results with real‐world data indicate that the pronounced dependence of mixing depth on light extinction is a general phenomenon which cannot be ignored.