TY - JOUR
T1 - A study on the role of hydraulic retention time in eutrophication of the Asahi River Dam reservoir
AU - Kawara, Osami
AU - Yura, Eisaku
AU - Fujii, Shinobu
AU - Matsumoto, Toyohisa
N1 - Funding Information:
Thanks are due to our col1eagues who contributed their sustained efforts and grasp of objectives to the accomplishment of the observation program. This research was sponsored by Electric Technology Research Foundation of Chugoku.
PY - 1998
Y1 - 1998
N2 - 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.
AB - 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.
KW - Asahi River Dam reservoir
KW - Eutrophication
KW - Growth rate of phytoplankton
KW - Hydraulic retention time
KW - Numerical simulation
UR - http://www.scopus.com/inward/record.url?scp=0031946768&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031946768&partnerID=8YFLogxK
U2 - 10.1016/S0273-1223(98)00030-4
DO - 10.1016/S0273-1223(98)00030-4
M3 - Conference article
AN - SCOPUS:0031946768
SN - 0273-1223
VL - 37
SP - 245
EP - 252
JO - Water Science and Technology
JF - Water Science and Technology
IS - 2
T2 - Proceedings of the 1997 1st IAWQ-IWSA Joint Specialist Conference on Reservoir Management and Water Supply - An Integrated System
Y2 - 19 May 1997 through 23 May 1997
ER -