INJECTION OF HIGHLY OXYGENENATED WATER INTO THE BOTTOM OF DREDED AREA IN LAKE NAKAUMI

Abstract

A field test of supplying oxygen-rich water into the bottom of dredged pits in Lake Nakaumi was performed in 2009. We used recently developed hypolimnetic oxygenators called WEP. In Yonago Bay, we selected two adjacent dredged pits, then installed and operated the WEP system in one pit for the experimental purpose. The other pit was used for the control purpose. The vertical profiling data of water quality in the pits showed the dissolved oxygen concentration was increased to 15-29 mg/L nearby the outlet of WEP system, and was kept at 5-15 mg/L in the experimental pit, on the other hand it was less than 5 mg/L in the control pit for 6 months of the experimental period (May - Oct.) in spite of the existence of tidal current. Moreover, we performed 3-D numerical simulations using ELCOM to evaluate the flow characteristics in the pits. They revealed that the water in the bottom of the pit stayed still but the water in the shallower layer there sometimes flowed out to the surrounding area.