A study on the role of hydraulic retention time in eutrophication of the Asahi River Dam reservoir

Osami Kawara, Eisaku Yura, Shinobu Fujii, Toyohisa Matsumoto


61 被引用数 (Scopus)


The Asahi River Dam reservoir is one of the important freshwater resources for Okayama City, Japan. The eutrophication of the reservoir has been warned of since the 1980s. In this study, we discuss the relationship between hydraulic retention time and increase of phytoplankton, and the influence of wind-driven currents on the spatial distribution of phytoplankton based on the observations and numerical simulations. Observations were carried out from 1993 to 1995. The numerical simulation of hydraulics in the reservoir was carried out by applying an orthogonal curvilinear finite difference method. Judging from phosphorus and nitrogen concentrations, the water quality of the Asahi River Dam reservoir is usually eutrophic. However, high concentrations of chlorophyll-a are not always observed. The observed dependence of chlorophyll-a concentration on hydraulic retention time is reproduced fairly well by a simple relationship derived from the balance of phytoplankton based on the assumption of complete mixing. The hydraulic retention time is a limiting factor of an increase in phytoplankton in the Asahi River Dam reservoir. It takes a retention time of 2 weeks for the sufficient increase of phytoplankton. The results obtained by the simulations show that the wind-driven currents play an important role in the spatial distribution of phytoplankton.

ジャーナルWater Science and Technology
出版ステータスPublished - 1998
イベントProceedings of the 1997 1st IAWQ-IWSA Joint Specialist Conference on Reservoir Management and Water Supply - An Integrated System - Prague, Czech Repub
継続期間: 5月 19 19975月 23 1997

ASJC Scopus subject areas

  • 環境工学
  • 水の科学と技術


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