Abstract
Phosphorus concentration in lake water (C) is described in the following equation, C = Lp × πr = Lp X Rp/Rw, where Lp is the concentration of phosphorus in inflow water and πr is the ratio of residence times of phosphorus and water (Rp/Rw). Characteristics of seasonal changes and variation of πr were studied in Takahamairi Bay, Lake Kasumigaura where is the typical example of shallow eutrophic lake in Japan. Phosphorus concentrations (P) in the most inner part of the bay where is strongly affected by the inflow of rivers was predicted from the following equation, P = 0.5 Lp. That concentration in the central part of the bay was predicted from the following equation, P = Lp x (0.18 + 0.025Temp.), where Temp. is water temperature (°C). Chlorophyll-a concentration in Takahamairi Bay was predicted from the estimated phosphorus concentration and from Lp and water temperature.
