Abstract
Attenuation of incident solar radiation in Lake water without spectral separation was measured and analysed. Measurements were made by an underwater solarimeter specially designed for this study. Relative intensity of irradiance in the water was analysed in terms of Secchi disk transparency, and it was found that irradiance in lake water could be expressed by non-dimensional depth related to the transparency. The magnitudes of dimensional and non-dimensional extinction coefficients were also investigated, and the findings showed that the non-dimensional extinction coefficient in the deep part is about 1.5 per unit Z* for both whole wave-length range and 550 nm range of the solar radiation. It is assumed that the transparency reflects the overall factors which control the attenuation of solar radiation in the lake water.
