Model of light penetration in a turbid lake

Abstract

The relationships governing the penetration and attenuation of light in natural water bodies are of great importance to studies and models of photosynthesis and water quality in general. Quantitative expressions which give the rate of reflection of incident light at a water surface and absorption and scattering of light by suspended inorganic (clay) particles and by suspended organic particles (phytoplankton and detritus) in the water are developed herein for Lake Chicot, a highly turbid lake in Arkansas. Differentiation between inorganic and organic types of particles reveals their respectively different effect on light penetration. In addition, light attenuation is also a function of wavelength. Therefore, three wave bands are distinguished. In addition, light as seen by flat plate sensors and spherically integrated light as experienced by an algal cell are distinguished. To facilitate modeling of planktonic photosynthesis, a relationship between incident total radiation measured above the water (as available from a weather station) to underwater photosynthetically active radiation has been developed for Lake Chicot. The work described was exploratory and relied exclusively on Lake Chicot data. The results were intended for use in a water quality simulation model.