VALIDATION OF A RADIOMETRIC COLOR MODEL APPLICABLE TO OPTICALLY COMPLEX WATER BODIES

Abstract

A radiometric color model relating the color of optically complex (non-Case I) waters to the organic and inorganic color-producing agents (CPA) responsible for that color has been previously applied to the waters of Lake Ontario, Canada and Lake Ladoga, Russia. Additional underwater optical measurements and water quality data from Lakes Erie and Michigan and several boreal lakes in northern Ontario, as well as comparable data from the European lakes Krasnoye, Zug, and Lucerne are utilized to illustrate both the validity of the model, as well as the universality of its application. It was found that, due to the limited availability of specific spectral scattering and absorption properties (optical cross-section spectra) for CPA indigenous to natural water bodies on a global scale, the use of optical cross-section spectra appropriate to the CPA indigenous to Lake Ontario and those appropriate to the CPA indigenous to Lake Ladoga provided a more-than-adequate surrogate for the water bodies considered herein (inclusive of river systems in the British Columbia Canadian Cordillera for which results of a study relating river water color to hydrographic basin features are also revisited). Similarities among the optical cross-section spectra pertinent to freshwater biota and similarities among the optical cross-section spectra pertinent to freshwater dissolved organic matter would appear to allow such a liberal use of site-specific aquatic optical properties. However, greatest discrepancies in indigenous inland water CPA optical cross-section spectra are consequences of global geologic diversities. A compensation for geologic diversities is illustrated by the use of Lake Ladoga cross-section spectra with the European lakes and the Lake Ontario cross-section spectra with the North American lakes, also providing validation of both the radiometric model and its universality. Such geologic similarities could alleviate labor-, time-, and cost-intensive determinations of optical cross-section spectra for many inland water bodies.