Author(s): Makoto Takeda; Atsushi Tatematsu; Naoki Matsuo
Linked Author(s): Naoki Matsuo
Keywords: Nagaragawa Estuary Barrage; Water Quality; DO; Phytoplankton
Abstract: The Nagaragawa Estuary Barrage was built in 1995 for prevention of damage from a salt breeze caused by entering saltwater due to the dredging. After construction of the Nagaragawa Estuary Barrage water quality problems (the decrease of the dissolved oxygen (DO) in the downstream area and the increase of the phytoplankton in the upstream area of estuary barrage) occurred sometimes. In this study, the water quality changes from 1994 to 2005 are examined by the Nagaragawa monitoring data. It was shown that the change of phytoplankton density is influenced by water temperature and sunlight strongly and by river discharge, and that the DO is influenced strongly by the density stratification. Moreover, the influences of the barrage gate operation to the phytoplankton and the DO are also analyzed. The phytoplankton change in the upstream area of the estuary barrage is discussed under the same water temperature conditions. On the other hand, the DO change in the down stream area of the estuary barrage is discussed under the same water level conditions. From these examinations, it is cleared that the gate operation do not affect to the phytoplankton in the upstream area strongly. Moreover, the DO in the downstream area of the estuary barrage decreases by means of the flush gate operation with adequate discharge.
Year: 2009