Installation Of Deep-Sea Water Supply Pipeline For Mariculture And Long-Term Current And Temperature Observations At Bottom Region

The first facility 2650 m pipeline length, 125 mm inner pipe diameter of pumping 460 m3/day of deep-sea water from a depth of 320 m to shore for mariculture experiment utilizing deep-sea water in Japan was completed at Muroto, Kochi prefecture in March, 1989. The severe wave conditions that existed during a typhoon at this pipeline installation site required the pipe material which can endure high waves. And also, it was required to lay the pipeline accurately and quickly. It was determined that the most suitable material for the deep-sea water pipe was high-density polyethylene with steel wire armor in consideration of severe wave conditions due to a typhoon, and the optimal laying method was the reel-barge method on the basis of the pipe material and the conditions at the pipeline installation site. It took two days to lay the pipeline as almost planed. After laying and in order to avoid damage from high waves and anchoring, the pipeline was buried at a depth from 9.5 m to 60 m. As soon as the deep-sea water supply pipeline was installed, measurements of current velocity and water temperature in the vicinity of the deep-sea water intake were made for a period of approximately one year from December 7, 1988 to December 15, 1989 by a current meter with a water temperature sensor moored to a float 30 m away from the deep-sea water intake. The current meter was a rotor type containing a recorder, with data on current velocity, current direction, and water temperature taken for 10 minutes from every hour on the hour sent sequentially to the recorder. Approximately one year later, a cut-off device was activated and the recorder was recovered.