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

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)245-252
Number of pages8
JournalWater Science and Technology
Volume37
Issue number2
DOIs
Publication statusPublished - 1998

Fingerprint

Eutrophication
Phytoplankton
Dams
eutrophication
dam
Rivers
Hydraulics
phytoplankton
hydraulics
river
wind-driven current
Chlorophyll
Spatial distribution
chlorophyll a
spatial distribution
simulation
Computer simulation
finite difference method
Finite difference method
limiting factor

Keywords

  • Asahi River Dam reservoir
  • Eutrophication
  • Growth rate of phytoplankton
  • Hydraulic retention time
  • Numerical simulation

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

A study on the role of hydraulic retention time in eutrophication of the Asahi River Dam reservoir. / Kawara, Osami; Yura, Eisaku; Fujii, Shinobu; Matsumoto, Toyohisa.

In: Water Science and Technology, Vol. 37, No. 2, 1998, p. 245-252.

Research output: Contribution to journalArticle

Kawara, Osami ; Yura, Eisaku ; Fujii, Shinobu ; Matsumoto, Toyohisa. / A study on the role of hydraulic retention time in eutrophication of the Asahi River Dam reservoir. In: Water Science and Technology. 1998 ; Vol. 37, No. 2. pp. 245-252.
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